But drivers aren't locked in to a single service, and there's little to no cost for drivers to be on both Uber and MyStartup, so the network effect is diminshed.
You should read more into this, but even though switching seems easy in theory, the truth is different. Going through another driver application process / training takes time, and even then using two apps creates extra annoyance. You would be surprised how lazy People are even if there was a way to grow their earnings through switching.