I thought I just said this, but I will say it again in a slightly different way.
Lyft and Uber have taken a huge percentage of the _entire taxi cab and black car service industries_. To the point where they may very possibly entirely replace them.
That is why those companies have large valuations.
The reason people use Lyft and Uber is the same reason people use taxi cabs. They went out drinking and can't drive home, or never planned to drive home.
Its true that people with disposable income are also a large user base.
Also in my area of southern California and many other areas, the buses are horrible and only students, homeless or poor people use them. Almost literally. And their routes are limited. Everything is massively spread out around here.
Personally, I had to sell my car, and I have zero disposable income. I just use Lyft now because it is cheaper than a taxi and arrives much more quickly. I also very rarely go anywhere far. Last two times I went to the store I walked.