Because I don't want my ability to go wherever I want to go to depend on not violating whatever Toyota decides their terms of service are that day. That or say you're in China and cars stop coming to you because one of your social media posts dropped your social credit score below the threshold.
Why would you not just own a car that gives you the option of manual and autopilot?
I think there's room in the world for both. Fleets of cost effective, low environmental impact self driving cars are a pretty straight line (and less exploitative) evolution of "ride share" services, and would layer very well with expanded public transit systems and standard rentals to make life fully accessible without car ownership being a necessity.
But for those of us that live rurally or otherwise have the need- we drop the cash and own.