Let's forget the regulatory (AOC etc) and ATC issues for a moment. The technology being spruiked by the likes of Uber may well eventually be mature enough to attain certification for use in carrying fare paying passengers.
However there is a major difference between Uber Air and the Uber "taxi" service being offered with motor vehicles. When it came to the original Uber service there was already an well established demand for this type of service at a price the man in the street was willing to pay and an existing certified product - the motor car - for delivering the service. There is pretty well no current equivalent to the proposed Uber Air. Not only do they have to perfect the technology they wish to use, they also have to create a market or a demand for the service.
There is currently technology available (helicopters) that can provide an Uber style air taxi service but there is no service. Why? No one is willing to pay what it costs.
Uber and friends think they can develop new technology that will will reduce the cost to a price the masses can afford. I say they are dreaming. Unless they can find a way to make the costs affordable to the masses they are wasting their time.