It could be due to the fact that the Surface devices and the Office are developed by two different divisions in Microsoft. The group developing Office may not h

It could be due to the fact that the Surface devices and the Office are developed by two different divisions in Microsoft. The group developing Office may not have a huge incentive to create ARM version just because another division decides to go with ARM processor on a new device. Also think about anti-trust! If Microsoft could develop ARM version of Office in secrecy for the Surface launch, it would not give sufficient possibilities for Office competitors to do the same.