Why would they want to pay people who aren't actually doing work? That's the point if they are forced to take full-time employees, those employees should be working all the time, instead of at their leisure the way it currently is. There is no requirement to take a ride if you don't want to right now, but if there's surge, drivers will be encouraged to work. If they are full-time employees, they just work for a flat rate and at the places and times that the employer requires them to be, in order for them to be maximally used.

Hiring people to just sit around and do nothing doesn't make any sense whatsoever.