How much wear and tear for a robot that is just sitting still listening to the internet uplink? If only every tenth of all cars currently stored on public parking would be hailable robots you would get very comfortable availability even in the remotest village. Occasional idle rebalancing drives would probably be less common than the idle leg of current “go pick someone up“ or “bring someone somewhere and return" trips.

If robot taxis happen, they won't be just like regular taxis without a driver. The mix between investment, hourly cost and per mile cost would change a lot, making entirely new business models possible and shifting the optimization peaks of existing ones.

Personally, if I would somehow happen upon a dozen robot taxis to turn into a business, I would select elderly people in a rural area as my target audience. Not your typical early adopter and quite some natural churn (short age window between should not drive anymore but still able to take care of themselves), but you get awesome ad targeting if you put out flyers in the doctor's waiting room. Oh, and you need to hire the one taxi driver who currently serves the doctor's appointment market in that area as your support guy who chats all the nice old ladies through the introductory phase over the car's hands free.