Why?

You know those stores where, when you go to try on clothes, they give you a little plastic thinky labeled with the number of items you are taking with you into the dressing room? Why is it that when you are going into the dressign room they count your items as if the future of the entire free world depended it, but when you come out of the dressing room they just take your number back and pay no attention to the number of items you are returning?