Because MS has a stranglehold on Epic. Gears of War is selling XBox360s like hotcakes and MS is loving the current and future dough. If there was a PC version less people would commit to buying a 360 (and subjecting themselves to xbox live) to play it.
Eventually it will come to PC I beleive, but it's going to be a long time coming.
Eventually it will come to PC I beleive, but it's going to be a long time coming.