> More drivers in the network makes it faster to get a ride and therefore more attractive to riders.

All else being equal. A competitor boasting "hey, we're just like Uber, but with longer waits" probably won't get far. They could compete on

* lower price (fixed rate vs dynamic pricing, like Wingz)

* higher class of the vehicle

* support certain edge cases like kid-friendly service, bilingual service or women driver (hat tip Bojack Horseman Season 3 for that business idea)