Uber can't afford to run a national taxi service at scale for the same reasons no one else has ever done so. The economics of a taxi fleet don't scale to that size. Owning their own autonomous vehicles would only further erode their non-existent business model.
> The economics of a [self driving] taxi fleet don't scale to that size.
I'd be interested in hearing your analysis! I haven't heard that one. Tesla claims these vehicles will pay themselves off within two to three years once they can operate fully autonomously.
Although I've often speculated if you could have had an Uber-like service in the 80s, where you register with your credit card on file, and then call a number with a location to get an estimate pickup, and then they page a driver to get you, perhaps with an authentication code.