Uber is at it's core a tech company, its valued by market position, brand value, userbase, software and data assets, engineering talent and other connections dealing with relevant parties. It's worth a lot by those metrics and it would be very hard for any other tech company to make significant inroads against them. Longer term prospects are the expected money makers, areas they can branch into, data they can use to gain competitive edges in other market etc.
Uber driving to me is not very different than Youtubing. It's a sorta new societal thing where you work on top of a platform that you have little say in. It can make changes that disrupt you, but you can't really affect it to any strong degree. The trade off is it also makes no requirement of how you operate, you can use it as much or as little as you want. And there's also the question of if these new sorts of jobs must naturally be sustainable. That is, if you quit your day job, do they have any obligation to make sure you have a livable wage? And that is a more difficult question than I think a lot of people realize. Certainly I don't think just because you do something means it must be sustainable but I also expect that they shouldn't misrepresent the work and pay either.