Win2k/xp was around for so long, many users got so used to it. MS have the wrong idea about OS development. You can make an OS prettier, but as with office 2003 vs office 2010, moving everything around just confuses people.
With support dwindling for XP, I have actually switched quite a few clients to YLMF linux, a distro which is an exact clone, to the point some professionals cant tell the difference of XP.
For many it's a no brainer, why on earth would they start learning all over again and take 10 clicks to do something on win7 than 5 clicks on XP, have to upgrade their hardware and pay a large sum for the privilege with no benefit offered to the average end user?
MS, as a company, really are a load of brain dead turnips. Actually, in the recent discovery that plants may indeed have feelings, I feel that's offensive to turnips.