Some of which are exclusive to pre-orders and of those some are exclusive to certain retailers.
Grid 2 was released with 3 day-one DLCs and here in SA BT games, kalahari and Takealot had different packs. Thus if you wanted the asia pack then you were stuck with Kalahari. It is in essence a Monopoly and for people like me who can't download a game with all 3 off steam like me it sucks.
Edit:
Also what's the point of having consumer rights legislation written to protect you when your gonna roll over and say "meh I'll pay more for a DLC"