Why? Because it runs smooth, it's stable and it has not much crashes
It's about useability rather than being up to date. If you aren't dependent of windows (because of your work or so), you can do everything on it (except the newest games and so).
*sigh* it's just so much fussing around with sh*t of these pc's! I do not want to know the amount of burnouts due to this.
btw see also my thread about spyware in bios (!RANT!)