so the car isnt damaged when its sold on. Nobody wants to buy a car with a broken window. Its also easier to steal, doesn't attract attention and id guess has a high success rate.It seems really stupid really... i mean if you were going to steal a car, why stick a peice of paper in the window, wait for however long in the bushes (as you dont know how long they are going to be!) and then jumping out and reverse over the person who owns the car, who seems to not see you get in to you car...