When I was in college I worked nights in the downtown are (Kansas City) in a not so nice part of town. I never had anything of value in my car so I always left it unlocked.
One night after work I get in my car, look over and the passenger window is smashed. Nothing taken but nothing in the car to take. $50 for a new window and a pain in the butt to replace.
Just open the door, fool!! It's unlocked!

Nothing worse than a stupid thief.