Retailers can use economies of scale to lower prices and increase variety of products. There are no economies of scale in Uber the way it's structured now and the service is largely homogeneous. There could be economies of scale with self-driving cars, but why should they be the winner there?
The only way they managed to offer lower prices (which is the main concern to riders) is through VC subsidy. There is simply no way to significantly lower prices for taxis, unless you have self-driving cars.
The only thing Uber has is a limited power of a local network effect which is a relatively weak moat.