Look at all those phones!
It’s unlikely that every single one is running a different car-service app, but there are enough operating in San Francisco that it could be: one for Curb and one for Flywheel, the two taxi-backed apps, and another for Uber, which also dispatches taxis. If this were a livery car and not a cab, it could also be running Lyft. And of course, the cab is probably accepting radio dispatches from a local service, as well as picking up street hails.
This is what it looks like when you pump lots of competition into the car-service marketplace: Suddenly, there are lots of ways for drivers to find a passenger, and you’d expect drivers to maximize their revenue by choosing the highest fares or the most convenient pick-ups to increase turn-over, whether that’s through Uber or another service. Pretty soon, drivers may need a way to aggregate all this competition.