Consider a place like gamestop. When you walk into there, where are all the new games? WAY WAY back on the top of the back shelf, and up front is the bargain bin, old games, used games. Game developers make no money from purchase of a used game (there are no royalties or anything like that for used games [as it should be, IMO]).
Places like Gamestop make all their money by buying up used games cheap and selling them for way more than the cost they bought them for.
A used game is usually (marginally) cheaper than a new one. This steers your average gamer into the bargain bin vs a new game, but this one-time content would be an incentive to get a new game for some bonus stuff.
I hope this is only used to offer BONUS content as a reward for buying new, and not reduce functionality. E.g. none of this: 1) You can't play this game because it was already 'activated' by someone 2) You get this crappy version of the game because it was used -Dom