So: When a cop hauls one in, the judge has to give some penalty. A few nights in jail on the third or greater offence and they don't visit the town. ONE judge should handle (sorry!) all prostitution, so they can track. Also, cops don't try unless the prosecutors and judges try too. There's more coordination required here than it sounds like.
Some social service agency/chruch group has to help some (can't do all) of the girls, usually younger and on drugs.
It's worked to some degree in DC, believe it or not. Not glorious, and not good enough for political grandstanding, but it does make a really noticeable difference.
The judges across the river in Ohio do not take prostitution seriously.