Movies take up shelf space because they want them to, not because they have to. The packaging is a big deal. If this were not the case, they would simply keep the discs in envelopes. Even in game-stores, they put EMPTY BOXES on the shelf and keep the games behind the desk. Why would they put empty boxes out there if retailers didn't like to waste the shelf space? It's because having the pretty box sitting there in plain sight helps to sell the product. Retailers don't want to get rid of shelf space, because as soon as shelf space doesn't matter, they go out of business, because that's the value-add they bring to the equation.