I'd only call that "fair" if they assume the position of an actual employer at the same time, offering all the usual benefits of an employment to their employee drivers, especially including a minimum income. If they did, they were free to distribute work as they like, by any crude criteria imaginable, because it's not at all illegal to fully pay an employee for essentially doing nothing. But that's exactly what they don't want to do.

They want to have their cake and eat it, too.