In America most folks buy and own their stuff. Boats, RV and such is a good example. They view their cars as part of their nest (me too).
Now in other cultures, especially where incomes are lower, yes using sw to call a FSB car would work. Rental agencies will be in competition with individual owners. Just saying FSB robo taxis might not be as big as Musk thinks. He thinks money saving will drive the market. I don’t see that as a strong part of the US consumer market.