Short term? Cash. Long term, nothing.The idea of FSD - and selling that idea while taking in tens of thousands of dollars per customer - is more valuable to Tesla than actually implementing it.
If they were on the verge of a true robotaxi / robotaxi network, why would they give up some % of that profit to owners of the vehicles? Elon said in 2015 (? The year escapes me but it's been awhile) that they had an automated snake charger. So if the cars can drive themselves and pull into a Supercharger stall and get a charge autonomously, why go through the mess of splitting things with current owners? After all, the net present value of FSD is "on the order of a couple hundred thousand dollars," per Elon. It seems more valuable to capture 100% of that rather than split it with an owner for $12k or $200/month.
Also, medium term there is more value in building out factories than there is in owning the fleet. Tesla is better off selling cars that can be taxis to customers and getting paid for the car with a profit, and then taking a cut of the taxi service fees and spending that money on more factories or more R+D.
Long term that might not be true. Or maybe the banks will start tripping over themselves to give tesla loans to build those robotaxis, but rates are ridiculous right now.