Yeah, there are labor laws for a reason and if you're using "contractors" you don't have to pay minimum wage for example. There are some Uber drivers that have learned how to game the system and earn OK money, but they work hard and hustle customers.
The average Uber driver probably makes less than minimum wage, - especially once their expenses are factored in. Uber pays a premium for working certain hours, accepting 90% of rides, taking at least one ride per hour in that time frame, etc. It's hard to qualify for the premium all the time.
So really what it amounts to is that Uber is dancing around labor laws so that they can offer a cheaper and more convenient service. There may or may not be evil intentions, but that's the end result.
I guess the question is when does an arrangement for services cross the line into exploitation? It's not always obvious. I may be perfectly happy to do something for a few bucks on the side or even for free just for the experience or the kicks. But what if someone else is trying to earn a living doing the same thing?
For example, let's say you'd think it be great to sail across the Atlantic on a 70 foot keel boat but you lack experience and a boat. You run across someone advertising the need for crew on a two month sailing tour, - no experience necessary. You have to help pay for food and supplies, plus you have to help sail and maintain the boat along the way. But otherwise there's no charge AND no pay. Sounds like quite an adventure right? Well, a week into it you discover that there's a whole lot of work to do and the "captain" isn't doing much of it. In fact, he's got paying guests that aren't doing anything at all. You want off but the best he'll do is drop you at the next island and you've got pay for your own way home.
Well, there are laws that govern this kind of thing because it is very easy to exploit people.