X/Y's main purpose in the US will be selling the system, unlike B/W which was a game released for a system that had the userbase already present and anticipating.
Usually, it's rare to see people preorder games for consoles they don't own, and a lot of them think with the mentality that "I'll pick up a copy along with a 3DS/2DS at launch"
This can slightly relate to why Japan has so many preorders, considering the overlap of different gaming audiences there, unlike the US where pokemon gamers are a category of their own.
