Taxis in general don't fully turk the concept, at least not in areas without reliable taxi volume. It's reasonable as long as you can rely on the taxi to show up within a decent amount of time of requesting it or expect to see one in passing in a short amount of time.
Uber et al. have done a lot to help with this in my experience, but I've had many times where I'm in a location that taxis aren't typically in the immediate vicinity. Calling the cab company has often led to lots of waiting, not knowing when the car will get there, with cars sometimes never showing up at all. Knowing that the car is definitely coming to you (whether it's a self driving car, Uber, or any other service that tracks the vehicle's location) help remove that uncertainty and definitely makes it an acceptable option in more areas.
That reliability and knowledge justify the extra cost for taking Uber (or requesting a self driving car some day) to me, more than the comfort or style of a town car compared to a cab.