You also have existing taxi companies to compete against. Way before Uber was a thing, my preferred company in Stockholm had a simple hailing app, it was basically one button for "I want a cab, here, now". No tracking, no payments, nothing fancy, but still.
These days, Taxi Stockholm has a hailing app that is on par with Uber's app, and I just can't see how Uber can compete with that. I can use Taxi Stockholm and get a professional cab driver in a nice luxury car that is insured, regulated, cctv'd and has a trusted brand name, or I can use Uber and get a non-professional in a regular car, no taxi license plate, unknown insurance situation, for maybe a cheaper price.
Uber is fantastically successful in places where the existing taxi market sucks for whatever reasons, but there are plenty of places where it doesn't suck, and it's very questionable what Uber can bring to the table then. Or Lyft, Hailo, etc. Any technology they make can be easily copied by their competitors, but local vehicle fleets can't.