Why? Because in their wisdom, the people of the state have chosen to make the behavior as illegal as possible without being totally illegal, and now they will have to pay the costs of enforcement.
I heard a recent story about a man urinating behind a grocery store. Now he's classified as a "sex offender" and must register his residence for the rest of his life. I heard a story this morning about a man who visited a whorehouse and was arrested. Since he was on probation for a different offense, this violated his probation, and now he's back in prison. So, as my friend Bill from Wnnco says, now society will pay $32,000 a year to host this prisoner who heretofore had a paying job, just because he paid to get his jollies in the wrong place.
Our prisons are full. We keep building more. Isn't there someway society could begin to make better punishments and better choices than just locking up anyone who might have infracted our particular whims?