From BBSpot.

11. Because prime numbers are inherently evil.
10. Because Bill Gates will give you a dollar if you use Firefox and email this top 11 list to 11 friends.
9. Because your pirated version of Windows won't let you install it.
8. Because some 13 year old in IRC said that IE7 was "teh scuk."
7. Because you'll have a hard time finding the new IE icon on the desktop.
6. Because it's no longer cool now that it's out of Beta.
5. Because they don't make it for Linux.
4. Because your son will yell at you if you do an upgrade without his approval.
3. Because Microsoft hasn't made a good browser since Netscape Navigator 4.0.
2. Because the Mac nerds already have enough reasons to beat you up.
1. Because there are plenty of known bugs in IE6. No need to get new ones in IE7.