I ride quite a bit - sometimes, for various reasons, I prefer to push my bike. I get many snarky comments about this, people demanding to know why I wasn’t riding. I didn’t think much of it, until I was pulled over by the police, and they hit me with the same paranoia. They were really convinced I must be up to no good, and kept reminding me of the fact that I chose to push, rather than ride, my bike.
So, is there some stereotype I’m unfamiliar with, a ‘‘certain type’’ of person who does this? 
Bicycle thieves, once away from scene of the crime. They may find the bike they just stole is not sized properly to comfortably ride and/or the seat needs to be adjusted.
It’s also possible the person walking the bike doesn’t know how to ride at all and is merely walking the bike from where they stole it.
bizarre
Let’s just say that bicycles thieves are not at the top of the criminal totem pole. The IQ requirements aren’t incredibly strict.
You don’t have to know how to ride a bike to sell one on Craigslist.
And yes, a disturbing number of people I know, knew, or know of, can’t ride a bicycle…
I think this is because people never get around to it when they’re younger, and then they’ve eventually passed the age when it’s socially acceptable to learn.
FWIW, I learned when I was 19. I was sick and tired of being looked down on for not being able to ride a bike, so I took it upon myself to learn.
Were you in a commercial district? Most anything you do out of the ordinary in a commercial district will raise the suspicions of cops.
I guess you’re SOL if you have a flat tire or other problem where you can’t ride.
No, the police stop, investigate, and move on. They are supposed to check out unusual and suspicious activity. It’s what we want them to do, in general. Anything out of the ordinary should get their attention, and as long as their investigation is legal and not harassment, it’s a good thing.
I was forced to learn by my dad, but I hated it so much I refused to do it again after I was pronounced proficient. I’ve probably forgotten it by now.
This could almost be a thread in itself, but…
How long did it take you to learn?
Did you fall over much?
Did you start with training wheels?
A Reporter Learns to Ride a Bicycle as an Adult --NY Times 08/10/12
Did the cop ask for your ID? Its well known IDs contain what bike you own 
I regularly cross an overpass with a very narrow sidewalk and two lanes of traffic whizzing by. I sure wouldn’t want to ride in the roadway on a bike and few do, but many ride on that sidewalk and expect me to make room for them to pass (often come up from behind too). It is illegal of course, but few will walk their bike across. SOBs.
Words to live by.
The police work for me; that’s what I pay them to do!
Would you make room to let someone walking faster than you get past? A rider on a bike is no wider than that, and considerably less wider than while pushing the bike from beside it? Would someone passing you while walking their bike be an SOB? What is it, the space they take up, the inconvenience of moving to the side, or just the fact that they are violating the law, that pisses you off?
A pedestrian takes up considerably less room than a cyclist trying to balance on a narrow sidewalk while avoiding:
Pedestrians must consider these obstacles as well but are considerably more nimble, maneuverable, and less likely to spectacularly crash than a mounted cyclist.
No but if someone actually bothered to report their stolen bike, and it matched the date and time of the stop, then the info on the id could be useful.
Also, if someone was a bike thief, then they may have a criminal record or outstanding warrants.