That's the market, if uber wants to scale they have to do that driverless.
Who will want to own, maintain, deal with parking, insure, etc etc a car for 10 years when you can have this year's model appear anywhere, anytime by just taking out your phone?
The 7k savings assume you bought a cheap car and kept it, I also did not factor tax & insurance. Savings increase dramatically if you were to finance a 35k+ 2nd car that many Americans in the burbs seem to do.
Uber doesn't "scale", there is no economies of scale that kick in anywhere in their business model.
Once Uber goes self driving, they take on responsibility for all of these logistical activities, and they currently have no capability and capacity to do that. These activities only scale so far.
Why would they need to do that. They're a software company, they have explicitly demonstrated no motivation to take on this work.
It's really not hard to envision them partnering with an existing bricks and mortar to provide those services - e.g. car rental companies provision through their hubs, or uhaul steps into the game and their franchise owners become uber hubs.
I really feel this is the obvious endgame, but who is to say.
As for scale? There very much is efficiencies to be gained in becoming a true mass transit system.
By 'at that price's I mean Uber have currently lost 15 billion dollars subsidising taxi fares. They cannot sustain that.
To the point of Uber maintaining driverless cars. What's to stop them going to a franchise model. Uhaul-like hubs where the cars go to get charged, cleaned etc?