True, it doesn't have to tell you when you work. But it does have to pay you a minimum wage. If a staffing company said: "work whenever and we'll pay you a minimum wage", then drivers would probably routinely drive at times they found pleasant, not profitable times for the staffing company. In this case the staffing company would start up restrict the hours a driver could drive.
A staffing company wants to reduce the amount of unprofitable hours driven. To do that they have to restrict working hours. It's not guaranteed but a highly likely outcome of the set up.
> ...then drivers would probably routinely drive at times they found pleasant, not profitable times for the staffing company.
Are you sure? Have you ever worked in a job at the mall that was relegated to telling you to "I dunno, why don't you come in when you're feeling pleasant or comfortable?" Similarly, airlines that schedule flight attendants don't tell them to come in whenever they want. You can fire people who are your employees, yeah? And you can pay people who outperform more.
Kind of dead thread but... If the company says to you: "you can work whatever hours you want!" And then turns around and says, "oh, but if you work those unprofitable hours, we'll fire you.." then how exactly is that not restricting the hours that you work? You can't have both.
A staffing company wants to reduce the amount of unprofitable hours driven. To do that they have to restrict working hours. It's not guaranteed but a highly likely outcome of the set up.