As it happens, prostitutes are punished for breaking the law, all the time. While living in Las Vegas, I read that the police were "slamming girls with jail time"...while in the rural counties, brothels remain legal.
But Vegas's "slamming girls with jail time" doesn't accomplish a whole lot, their pimps either bail them out, or not...and the girls won't 'roll over' on their pimps, that the cops are really hoping to bust.
So it's WHAM (gavel sound) "$500! Next! WHAM $500! Next! WHAM $500! Next!" If you made $500 a minute, what would be the enticement to stop? (Follow the money, as usual.)
Indeed, prostitution should be legal...it IS legal in the sense that some men won't get sex until they cough up a diamond.