All because many users don't care for Metro...
http://www.computerworld.com/s/article/9246991/Mozilla_shelves_Metro_Firefox_cites_user_apathy_toward_Windows_8
The MSO iPad apps function as "Office Readers", unless you have a 360 subscription. Not a stick in the eye, but not terribly useful by themselves, though I suppose you could put some Office docs on your iPad just to look at them or show them off.