One other reason why people are using Windows instead of Linux is the consistency. While there are some changes (xp->Vista->7) most of the stuff is still intuitive and most things are where they used to be.

On Linux, and particularly Ubuntu, the whole thing changes arbitrarily. This might be OK for some people, but some it sucks. I am pretty good with computers, been using them for 17 years or so. I am also a developer, and I am used to multiple OSes, and I still don't like changes for the sake of change.