Thats because people have their stuff in their car, and ultimately dont want to hang around waiting for a car to arrive.>>TLDR: By the time FSD becomes a reality, it'll be cheaper to hire than own.<<
Ignoring the wishful thinking before the comma <g> it's cheaper by far even now for most people to hire a taxi/rent for the day - but we don't. I can't see that changing.
As for FSD becoming reality, well it already is. Its an admitted marketting term (by tesla) designed to extract additional cash for tesla cars. Its working as intended. It promised full self driving under certain conditions such as traffic lights and freeway off ramps. (Refer website for what it will give you). You wont find anywhere on the website that FSD payment will eventually offer you autonomy or a robotaxi.