It certainly is true that many people have a nodding acquaintance with Microsoft products - although surprisingly few have mastered, say, 10% of their features. (Largely because so many of those features were added only so as to win tick-in-the-box sales contests). So, in the short term, there is some advantage in continuing with them. Just as there is some advantage in never training staff, just hoping to hire people with existing experience.
In the medium term, let alone the long term, such policies are very risky. The changes in UI between consecutive releases of Microsoft Office can be greater than those between an earlier version and an open-source alternative. As we have seen, many people baulked at the huge difference in UI between Windows 7 and Windows 8. And of course, if no one ever trains staff, eventually there will not be enough people with the necessary experience to go round.
Unfortunately our implementation of capitalism encourages extreme short-termism. Why not slash and burn while you are in a given job, as long as you can be fairly sure of getting promoted before the harm is noticed? Better still, your successor will look really bad, thus improving your image (relatively). And of course, if you accept the principle of never adopting any software that everyone isn't familiar with, by and by you will find that all your software is obsolete. As is your staff's experience.