Why would they not just take a cab, is that so hard to do? I can't imagine a cab not taking you for a short trip if you pay adequately?

I like Uber, Lyft and the like but I seriously only like them because of their vision that once self driving cars are available they become cheaper than owning a car.

The current advantages of Uber versus a cab are marginal, at least from my point of view (western europe, plenty of cabs). I would still always take an Uber if available, but if not I couldn't care less.