Sure, in dense metros like NYC you can say each Uber/Lyft is replacing a cab ride. I won't argue with you there. But in the suburbs, using a cab was not a normal thing to do, but using Uber or Lyft is.

Maybe I'm being too anecdotal, but I can only think of a couple of rides (out of dozens) where I would have called a cab had Lyft not been available.

Trying to get a cab ride from my house to a random place 15 miles away was a nightmare. Bad dispatch, no-show drivers, etc. Never really bothered after a few bad experiences, just designated a driver instead.

There are plenty of rides happening with Uber/Lyft now that just wouldn't have happened at all previously, not just gone to a taxi.

Assuming that Uber is either more convenient of cheaper than a cab, one would assume that the number of cab rides goes up.

Taxi cab drivers already work as contractors in many real taxi companies.

Uber did not invent this practice. They took it from the existing industry.

The existing industry was actually WORSE in that you would have taxi medallion owners who would charge people rent for the luxury of using their taxi medallion!

So please, do not blame Uber for the existing taxi cab contractor business practices.

I don't think that's entirely the case. It's true that taxi drivers in many markets are seeing less work because of Uber/Lyft, but many many many more people are taking Uber/Lyft than would have been taking taxis otherwise. I and literally everyone I know in SF are prime examples of that. (And I literally mean "literally"; there is not a single person I know for whom this is not the case.) People don't even think about ordering up a Lyft when they need one; they just do it. It's nearly as automatic as breathing. Attempting the painful process of getting a taxi was always pretty low on anyone's list of "reasonable ways to get from point A to point B".

(You can certainly argue that now having all these extra cars on the road is a bad thing, but that's a separate issue.)