It's an operating system, see?
And because it is an OS, I don't want to do anything with it. That's not what it's for. I do things with a web browser, word processor, games and my graphics suite. The job of the OS is to host these applications securely and without crashing and otherwise to stay out of my face.
As long as the OS can do that - and my highly customized version of XP does it very nicely thank you - why do I want to 'upgrade'?
Let's face it, there's been no killer app for the desktop in the past ten years. Only a few people do anything with the latest version of Photoshop or Word that they didn't do a decade ago (apart from using the despicable .docx format).
I've used vista and win 7 and get the feeling that the changes to the interface are mostly dumbing down the system so noobs can't screw it up. And if you've been using XP for a decade as many XP users have, a more 'intuitive' interface don't cut it. By now most XP users can operate their system blindfold.
Don't run it in admin mode, use good security software and a hardware firewall, and really there should be no need to change XP until a real paradigm shift comes along - and then win 7 will be obsolete as well.