The drivers are happy because they're healthy. They're making about $12 bucks an hour after the cost of driving is factored in. That's not enough to buy health care but it is enough to disqualify most from the subsidies. At those wages their paycheck to paycheck, and a car wreck with an uninsured driver away from disaster. Speaking of insurance those drivers aren't anywhere near as well insured as a traditional taxicab driver, which is another reason they can out compete taxis.
But there's another nasty side of Uber we haven't seen yet, which is that as work becomes more and more scarce you're going to see more and more people turning to it to pay rent. It's not so much the sharing economy as the desperation economy. That's the rub. Right now there are some drivers doing OK because $12/hour seems like a lot as long as nothing goes wrong, and there's plenty to replace them when it does. But it's a larger part of the race to the bottom that the modern world's caught up in...