There is a very low bar to entry when becoming an Uber driver, and so I would hazard to say that the vast majority of people who want to drive for Uber are already driving for Uber. So, if Uber were to suddenly drop all the current drivers, there would be no great rush of new drivers trying to fill the void. Just the opposite would happen, actually. The Uber drivers who had just been let go would switch to another service, and the folks who try to hail an Uber will be told there's a 2 hour wait for a car and so will simply take 10 seconds to close their Uber app and open their Lyft app instead. There's no possible way Uber could survive cleaning the slate like that.