In large portions of the South (Atlanta, all of Florida, many other places), we simply consider them suggestions, and not particularly useful ones at that.
Do you have any idea how LONG it takes to get anywhere if you drive that damn slow? If I drove from here to the Villages at the speed limit, I’d be eligible to move in by the time I got there! 
Let me make this even easier for you, then. Unless you are actively passing another vehicle, STAY IN THE GODDAMN RIGHT LANE.
That’s the law when driving on the Autobahn in Germany, and it is strictly enforced (along with a strict prohibition of passing on the right).
This rule is also a law in many U.S. states (though seemingly rarely enforced). For example, you sometimes see signs on U.S. freeways that say, “LEFT LANE FOR PASSING ONLY” or “KEEP RIGHT EXCEPT TO PASS” or “SLOW TRAFFIC KEEP RIGHT.”
I know, right? People force you to live far away from the places you actually want to be, and then force you to break the law and endanger others in order to get to those places in a reasonable amount of time. Obviously, your time is more valuable than some other person’s life.
Yeah, same story in Texas. It takes forever to get anywhere, and there’s very few cops who will stop you for anything less than 10 over.
And yes, robby that’s the rule I was really going for. If you’re not passing anyone, get over to the right.
I drive 65 in a 60 MPH zone routinely. The horror. Now I am become death, destroyer of worlds.
You are probably the dillhole going 15 in a 25 on a one lane road with 10 cars backed up behind you.
Here’s a chart showing each state’s “keep right” laws.
Here’s what the Illinois (my state) Rules of the Road says:
What isn’t clear to me is which lanes officially count as “the left lane(s)” when there are more than two in each direction.
And here’s an article from this January claiming that Illinois State Police are cracking down on “left lane lollygaggers.”
Well, I was being a little tongue-in-cheek, but it’s actually geography that makes stuff far apart. No matter where I lived there would be somewhere far away that I want to be at some point.
And who said anything about endangering? If everyone drives a consistent speed and obeys common-sense rules of the road (of which STAY RIGHT UNLESS PASSING is one of them), there wouldn’t be many problems. FWIW, even when driving 10 over the limit, my ass is in the rightmost clear lane where it belongs.
I would offer that during the summer on I-75 south of Lake City, the guy driving 5-10 under the limit in the middle lane pacing a car next to him (when everyone else is limit-to-limit+10) endangers WAAAAY more people than the guy going 20 over in the left lane. And you see it ALL THE TIME!
In the case of Illinois, it looks to me like it is talking only about the far left lane.
The “(s)” does not exist in the actual statute posted on the Illinois General Assembly’s website.
Here is the full text of the relevant part of the statute:
That said, best practice is to keep as far to the right as conditions allow. Nobody expects all of rush hour traffic to cram into one lane, and nobody expects you to merge to the right if doing so would block cars merging from a nearby on-ramp. But you shouldn’t go any further left than you need to, either, in my opinion. If you can safely maintain your desired speed in the far right lane, then there is no reason to move to the middle or left.
Based on my observations of this behavior in Europe: most people camping in the middle lane just zone out, I think half of them are somehow doing something on their phone.
The behavior seems more pronounced in people on their daily commute.
I notice this all the time as well, and I like to stereotype cars.
It is absolutely always fucking Prius, Scion Xd, or Honda Element hipster soy-milk wagons that do this middle lane hogging. When I see one of them in traffic, I get in another lane no matter how bad the traffic is and my lane will move up faster.
It’s always the typical Costco Trip “SUV” that is drifting in and out of lanes and always the damn Subaru WRX’s who think the Expressway should be a scene from Fast and Furious.
Cabs do all of the above, as well as the “i’ll drive partially in the off-ramp lane and cut back in to get ahead, then cross 3 lanes without pause or signal”
Only solution is to weave through and have a fast/powerful vehicle that can overtake others. Just pause when you weave instead of jumping lanes in one go. Safer and at least looks legal.
I notice this too. My kids say, ”Are you saying that all Prius drivers are clueless butt-heads on the road?”
I reply, “No. I say that if I spot a clueless butt-head on the road, then it’s highly likely they’re driving a Prius.”
I also add, “That’s an important distinction.”
I thought they were almond-milk wagons. 
Not to let the shitty drivers off the hook, but this kind of behaviour can be induced by lousy road design. I leaned about this in usability training.
For example, around here people have been conditioned to drive in the middle lane because the left and right lanes close often and people get trapped in them. Or suddenly you’ll come across a situation where both lanes on the left or right are mandatory turning lanes, and if you are in the far lane you are suddenly trapped and forced to exit if the road is busy.
There are some roads around here where if you just want to stay on the road for a long distance you will continually find the lane you are in ending, and you have to move over. then that lane ends, and you have to move over again. Then lanes on the other side of the road start closing, forcing those guys to move over, and the road widens on the other side again. So drivers are constantly having to move out of the right lane, then move back over. I assuming this is because the road engineers just opened and closed lanes in ways that made it easiest to build the road, and not necessary the easiest or most logical way for drivers.
If you want to avoid all that, you just stay in the middle lanes, and that’s what people around here tend to do. The road system trained them into it.
That’s not really complete, though, because, for Michigan…
…which implies that if there are three or more lanes, you don’t have to keep right. Except, the law also say you have to observe signs (meaning, not see them, but do what they say), and our signs say, slower traffic keep right.
Effectively, even if there are three lanes (or more), and there’s a sign as indicated present, you still have to keep right.
Where I live, good luck with that. Leave so much as two car lengths and some lane weaver is jamming into that space.
Draw a Venn diagram. A big circle to represent Prius drivers, a smaller circle to represent clueless butt-heads. Overlap them so that the majority of the clueless butt-head circle is within the Prius driver circle, but most of the Prius driver circle is not overlapping the clueless butt-head circle. That might help illustrate the point.
Make sure you pull over onto the shoulder of the freeway before bringing out the giant compass and poster paper.
And if I’m on an unfamiliar road, I don’t know whether the road is like that. People who’ve run into one such situation while dealing with heavy traffic in an unfamiliar place are likely after that to go for a middle lane on any unfamiliar road.
I think some people who drive the same route frequently tend to assume that everyone on the road with them knows that road as well as they do.
A few years ago we were gathered for my brother’s funeral, a very solemn and unexpected occasion. Afterward we were sitting around the house drinking beers, and someone asked me how my drive across the state was. It’s about 120 miles of two-lane roads with long areas of no passing. I said, “It was OK until you got behind a group of ten cars, and when you finally get up to the slow car in front that’s holding everyone up, it’s always a Prius, trying to get another half a mile per gallon.”
My niece’s husband set down his beer, looked up, and said “I drive a Prius.” Everyone started laughing, and it brightened a sad day. So sometimes Prius drivers are good for something (i.e., ridicule).
But if you’re a Maddy Midlingerer, you need to move over, & then back at each entrance/exit ramp, & as SiamSam stated, middle lanes tend to not end. It’s easier to just sit there & not worry about changing lanes. In light traffic, the middle lane is also safer in terms of having more reaction distance/time if you’re either using your portable handheld communication device or suddenly see an obstruction in front of you, whether that’s a deer or, literally, road furniture & need to swerve. IOW, I can see why people do it.
In the US, I’ll pass on the right. I love it when I can time it so that there’s also a car passing on the left at the same speed; guy in the middle feels like he’s going backwards. My experience on the autobahn is that even if i needed to slow down for a vehicle it was because said vehicle was passing someone else & would pull back to the right as soon as that pass was completed. Between the midlingerers & the left lane campers, sometimes the right lane is the fastest in the US.
As for Priui (Priuses?) I’m convinced they have a GPS related governor such that they cannot exceed the speed limit of the road they are on. I have seen them on expressways so I know they can go relatively fast but then they can’t even seem to do 26 in a 25 zone.
I definitely used to notice the thing about the slow driver likely to be in the Prius, but now that the Prius has been around for 20 years, or whatever, I’ve noticed a change. Some kid with an old Prius, that 10 years ago would have been in an old Corolla or Cavalier, is now in a Prius. And that person is weaving through traffic, and generally driving as poorly as anybody else, because the Prius isn’t a “green” statement to him, just an under $3000 car that was running.
Of course, in these parts the slow driver is more likely to be a 20 something male who waked and baked, instead of a retired person.