While you may be in the tiny-to-irrelevant minority of people in Beijing that use Uber and find it useful (probably mostly foreigners?), Beijing is not a normal Chinese city and in the scale of the Chinese market foreigners are statistically insignificant. I remain deeply skeptical "a car in five minutes" is reliably available in Beijing from Uber in many locations outside of the center of the city.
However, car-hailing apps make more efficient use of passengers' time, drivers' time, and cars themselves, compared with passengers calling a guy. Taxis make good use of drivers and cars, but waste passengers' time as they are hard to hail in many places in large cities.
Car-hailing apps are here to stay and, in the long run, some company will make money. Whether any single company will make monopoly-type rents due to being the only game in town, though, ...
Uber has _already_ generated non-zero revenues in China. I know because I have paid them money myself.
You are right that services like didi dache are head-on competitors.
You are wrong about calling a preferred driver. Sure, I do this when I want to pre-book an out-of-town journey or trip to the great wall.
But, if I want a car in 5 minutes, from a random part of town, there's no way I can achieve that reliably by calling a guy, even he has a 1st degree connection who happens to be 5 minutes away from my current location.