Self explanatory
Vista has higher requirements than XP, so what? Vista is modern, XP is 7 years old. In 7 years there is going to be a big jump in requirements.

the answer is by Aaron :
1: there are a number of old programs and old hardware that worked on XP but not on VISTA.

2: When vista first came out it was not as stable as XP, this has improved since the release of SP1.

3: the bad press from it have people cause people to think vista is made even when they never tried it.

4: Vista used more much more system resources then XP did and caused it to be slower.

5: The new user account control and other security functions has been annoying to many users.