This is not solely on Microsoft either; it's on Bungie. The game is not finished, they have all but stated this in the livestream. PS4 players do not immediately download the game when they pre-order; they get some kind of voucher on their account showing they have pre-ordered. Xbox users download the game immediately when they pre-order; thus, since the game is not completed we cannot download it yet, as this would force Bungie to release a large patch on day one. I would rather wait than to have to download a patch.