Don't remember the link, but Kalanick was recently quoted about how he'd buy a bunch of Tesla self-driving cars in 2020. Whether it will be Teslas or not, I believe it's clear that their whole strategy is to move to self-driving cars as immediately as feasible.
It's like saying, "whoa, tomato prices have skyrocketed -- I bet grocery stores are making record profits!"
To be sure, there might be some differential advantage, but not enough to justify subsidizing everyone in the hopes they won't jump ship after competition comes in from other brands without these "legacy costs".
Depends a lot on whether Uber themselves are making this happen, or we're looking to Tesla, Google, etc. If self-driving cars are going to happen anyway, then there's an argument from the other direction that permitting Uber has no long-term benefits.
Ignoring other car services, the public would have the option to buy their own self-driving car, but we'll get to the point where the majority won't. You'll be choosing between:
Own car - larger cost, garaging, cleaning, insurance, power, depreciation, fixed format (sedan, van, truck), etc.
Their car - pay per use, or subscription to use as required, hire the type of vehicle you need when you need it.
When the law catches up, insurance companies will have something in place.
When there's a large scale test, production/distribution have to ramp up.
Even if Uber can replace just 1% of their drivers with self-driving cars it would be worthwhile.