I wouldn't be surprised if it's also used by loss protection to make sure you stand in one place on the way in, and on the way out, as a way of making sure they

I wouldn't be surprised if it's also used by loss protection to make sure you stand in one place on the way in, and on the way out, as a way of making sure they get a clean camera shot of you. Loss Prevention will have cameras and sometimes plain clothes folks wandering around the store, and if they suspect you're up to something they can zoom in and follow you. Adding a step prior to exiting where your receipt is checked adds one more chance to confirm bad behavior, and gives LP time to zoom in on your cart and your face.