What reasons do you believe people are buying devices for it not the applications on them?
If you are putting the emphasis on app then I would point out that Office is used by almost as many people as Facebook, so an app is a bit of an over simplification.
For the record, I've heard variants of the exact opposite argument for why "people will never switch from iOS to Android", or "I could never give up $APP on my iPhone".
If Office really is that important to you, then yes, you might actually consider getting a Surface (tablet/laptop combo) instead of a Macbook and an iPad separately.
I'm pretty sure that's not true, and many people do very much buy a device for one killer app. Look at games consoles, if the tablet market alone isn't convincing.
However, I very much doubt anyone is going to buy a tablet-style device (of any brand) for this kind of application, because it's a silly kind of application to run on a tablet-style device.
If you are putting the emphasis on app then I would point out that Office is used by almost as many people as Facebook, so an app is a bit of an over simplification.