I'm Confused

A lot of Gamestop/EB supporters and employees are giving the defense that they need a display copy, yet they can't risk theft. This I understand, but I'm still confused...

Why can't they just create a cardboard mock-up of the box to display? My local EB is always filled with cardboard advertisements, etc., so it doesn't seem like it would be completely unreasonable. I mean, from the comments here it's obvious that the practice does bother many consumers.

Also, another question for anyone who may know. How many copies of any given game are typically gutted? I remember back in Nov. it was impossible to find a copy of Twilight Princess anywhere in town, but I went to EB games and they had an entire row of them. As soon as I reached out to even touch one, though, the guy behind the counter informed me that they were sold out. They had at least ten copies on the shelf! If they feel the need to put out a lot of copies to "advertise" the game, wouldn't a large poster or display do the same thing?