Nothing. It's legit doing this, and Bungie also announced months before the release that they going to release DLC. DLC these days is already in pre-production when the actual game is still in development. There are strict plans for such things. Years ago DLC was something which was based on feeback alone and never was planned. Thw developers created additional content because the fans who supported the game, wanted it. Nowadays DLC is part of the actual development cylce of the original game release.