This isn't making the point you think it is...

Uber doesn't buy the cars because it's not profitable.

They let the driver eat the depreciation, assume the capital risk, and deal with lemons and accidents.

No one drives Ubers thinking they're going to get rich, and I sure don't see companies buying up vehicle fleets to put into service on Uber.

Because it's a money losing proposition.

Why do you think Tesla is trying to also offload it onto suckers?

Uber doesn't buy its own cars because it isn't profitable given the depreciation and originally the higher risk of getting someone declared an employee. If they are choosing a car and losing money on it they are an entrepreneur. (Also Tesla doesn't want you to rent your car as that reduces their market so they want to sell another one in a fleet.)