Erm, because a lot of people get XP whether they want it or not? Try and find a non-'whitebox' builder who will sell you a computer without Windows on it. Oops, you can't.
Uh, YA WRONG!! There's a computer store here where I live that sells nothing but Linux based machines. They have no Windows products, and in fact refuses to install Windows on any machine if you bring it in.
Try not to use "finalized" words.....unless you know for a fact that you "can't" get it "anywhere".
If you want proof, let me know, I'll send you the address and phone number of the store....ComputeRX.
BTW: Not every "pirate" is using a "stolen" key... all ya need to do is change the way XP installs to a "corp" version, and use a legitimate corporate key.