As it is not supported anymore.
[citation needed]
You can go right ahead, I hope you like your screen door Internet security that XP has.
Anyone running Windows XP OOTB and connected directly to the Internet, I would agree is not the smartest. Windows XP with SP3 and up-to-date with all updates, proper security software, firewall on, and unnecessary services disabled, is about as safe as anything else Windows.
Myself, I'm running XP Pro x64. I'll move to 7 when I have to, but that's not right now. I'm hoping that before I'm forced to move to 7 (having to use it on a regular basis to provide adequate support) I might not being do the work I do now and can move to something else. I'd like to build me a Solaris workstation, again.