You all obviously haven't been to B&H
The store has conveyer belt gizmos running above people's heads for small things that are stored behind the counter - e.g. film - and an elevator system for larger items. While you can check out the demonstrator model, you don't have access to the specific item you're purchasing -- after the sales clerck writes you up, you go to pay at the front of the store, and then on to the area where you pick your merchandise up bagged or otherwise prepared for your journey out.
Within this system there's no spot where you can open a box, put fresh battery & card in the camera, and test it out.
The B&H system's a hoot to watch, and once you see the crowds and volume of business they do, you'll understand why there's no time to check the actual item. (The used counter is a different matter.)