Taxis in the SF bay area have always been a joke. The few times I've called them they often say they have no drivers in the area, or they claim they will send the driver but he never shows up, or they send one and it takes an hour. Hailing one in the street like NYC has never worked for me. There is no penalty to a driver if he picks someone up on the street before he gets to you, so they usually don't get to you. In Uber their rating would drop and eventually they would get fired. Not to mention Uber lets you order the cab without a call detecting your location, watch the car come to you on the map, communicate with the driver the entire time, and handles all the payment. So the innovation over taxis is enormous.