There is a big difference between someone going 10 mph below the speed limit because all the cars in his lane are doing so, and someone going 10 mph below the speed limit with 5 car lengths in front of him and everyone else in the lane doing the speed limit. You can tell by the large number of cars forced to pass this idiot on the right.
Urban interstates, especially during rush hour, are mostly driven by people who know exactly where they are going - though some of them seem to like to move into an exit lane at the last possible second. We don’t have left exits, so that isn’t an issue. Though I hate to admit that anything in LA is better than in the Bay Area, when I’ve been in heavy traffic there everyone moves along at a good pace, there is little lane changing, and things are less stressful than here. I admit that being two inches from the car in front of me and the car behind me is two inches from me is not stressful to me.
I used to commute on a bridge across the Bay, several miles long with no entrances or exits. You could easily see how people driving slowly in the left lane caused congestion, and the clog vanished past them. I would suspect that the accident rate on these roads is a function of the number of lane changes, because each is relatively risky. When someone has to pull from the left lane to a middle lane in traffic, typically those behind in the middle lane slow down, which causes a chain reaction of slowing.
Driving below the average speed in the left is selfish and obnoxious. If someone feels they must go slowly, they are welcome to the right lane.