Some prostitutes make a ton of money on selling their bodies. If you tried to tell them to stop they'd probably tell you to get lost. Some make 1-2 thousand a day. Lots. Others on the other hand make very little plus they have to split most of it with their sponsor(Sugar daddy). Sucks!
But on the whole i think it's up to the individual to decide if they want to do it or not, as long as they are not below 16-17. That's wrong.
They provide a service and get paid for it. With Full legalization they might earn more.