I had friend who is a state trooper and he said he NEVER lets a pretty female off from a ticket. He says then they call the station, file a complaint saying stuff like; "I think he pulled me over just to get a better look or flirt with me". Then when said captain asks if he wrote her up and he says "no", then it creates potential problems as to really why he pulled her over. If he ticketed her, than it removes doubt as to why she was pulled over.
Yup....even when they get a ticket, they will say, "Thought you guys did not give pretty girls tickets", and I say, "Yes, we don't".