Originally Posted by TWA Fan 1

It's the old principle of the carrot and the stick. They need something to entice you ("the carrot") and they do this with the lure of "unlimited free space-available upgrades." Of course, then, once they've hooked you, they apply the kibosh ("the stick"). Since the availability of inventory is all basically a fiction, the man behind the green curtain can do whatever he wants to make the most money for himself and the company.

If they were more straightforward about it, the "carrot" part of the game would not be nearly as effective...