Some situations in life seem to exist for the sole purpose of making you feel guilty for no reason at all. Seeing a police car just driving behind you, or catching the teacher's eye in an exam when you're just looking around will do it. Sometimes, so will getting your receipt checked before you leave Costco. After spending hours shopping, standing in massive queues, and wondering how to get everything back home, being stopped by a Costco employee who wants to check your receipt can feel odd, if not truly guilt-inducing. Why do they do it? Here's why Costco really checks your receipt before you leave.