You mean when Uber launched in San Francisco and was trying to bootstrap? Well, back then getting a taxi was difficult and unreliable. You could call ahead the day before for a 6am taxi to take you to the airport and have like a 30% chance that a taxi would actually show up. There was also no information passed to you as 6am got closer whether or not your taxi would actually be arriving, or at what time.

Uber provided reliable service, continuous stream of realtime updates, and an easy-to-use UI