Have you ever met an Uber driver who didn't give the impression that this was what he did all the time? I haven't, though I imagine not everyone is full time. It's quite a way from the idea that anyone with a car can give someone else a ride. For instance, I've never met a driver who happened to be going where I was going, or someone who thought they'd just make few extra bucks on their day off. They must exist but it seems to not be the norm.
At the same time, we're shoehorning old ideas of what's work into a modern setting, because it's reasonably quick to become a driver, and communications with the employer are minimal. Uber doesn't seem like the kind of firm where drivers might have a teambuilding excursion, though perhaps I'm wrong.