I disagree with this. I try to be pragmatic sometimes Microsoft knows they will not stop sales of iPad, just too many people jumping over the cliff after another follower. So if iPad sales will not stop, then those people will need something for presentations/documentations. If Office wasn't ported, then Apple would make their own software or those users on Google Docs would grow. Either case, it would eliminate the need for Office and dry up a lucrative Microsoft revenue generator.
So Microsoft is smart by porting Office to iPad. It shuts down Apple's plan of getting into document creation and mitigates Google Docs while at the same time increases user base for Office. Now on the flip side, I've thought about Cortana and I don't see any revenue protecting reason to give up Cortana.
I agree. I know that we sometimes question Microsoft's decisions, but I think they are correct in providing Office for iOS & Android. They probably calculated that not providing it would tend to pull users away from Office more than bring them to WP/Windows tablets. There are alternatives to Office. They're not nearly as functional, but they would suffice in a lot of cases.