There are a millions reasons but here's another.
Microsoft has a bunch of money because they take care of it. Why would they sink even more money into their games division which has lost them how much in the last 8 or so years? Even if they acquired those companies there's no guarantee it would make them much more money in the long term. Rare, cost MS nearly 400 million, were they worth it?
Furthermore, games companies are only as good as the talent the recruit and keep. If Microsoft acquired SE and EA I'm be certain there would be alot of people jumping ship.







