There are similar, smaller services (like Via, or myTaxi in Europe) that work fine and have nowhere near the money that Uber spends on their tech stack.

Ride sharing is extremely local, so it's not like you need any cleverly scalable tech. Most places will be tracking a few hundred cars at any given moment. Only in very large cities like NYC would you need to spend a little more on big servers.

What Uber presumably does is collect and analyze a lot of real-time data, which isn't strictly necessary to provide the service they're providing.