Scalpers run a business, making them unlikely to want to tie up cash in working capital for too long. Normal users, even those hesitant to preorder games, are far more open to locking up their cash in hardware preorders. After all, is it really that different to ordering hardware from a place with long shipping times? Would it therefore not make sense to open Steam controller up in preorder waves? It's obviously a worse deal than just buying the thing, but it's a far worse deal for the scalpers.