This is one of the few "themes" Hollywood knows - the others are "dumb military", "stupid fathers", "virtuous sluts", and "compromised people of faith". Oh, sorry, forgot "bad cops" and "powerful interesting crooks". Go eff yourself hollywood - we're tired of movies being written by drug addicted creeps with authority issues. Get some grown ups involved.
'Prostitutes with a heart of gold' are a mainstay of fiction. Dostoevsky comes to mind.