* License cost
* HDD / SSD storage space
* OS performance
* They might not agree with the EULA
* Or simply because they just don't don't like Windows.
The real question is now that the web has gotten everyone used to the idea of applications being platform agnostic, why would anyone want to go back to a Windows lock in?
All correct. Also, I booted into Windows on Saturday to play a game, it hadn't been booted in months, so I hat to wait for a forced SP install and Windows wiped out Grub. Every time I boot back into Windows it kills Grub and I have to fix it again. Not only did I lose all my gaming time to the updates, I lost extra time fixing my bootloader because of Windows' aggressive BS. The sooner I can get it gone the better and I'll free up an entire SSD for games.
On the other hand, having easy (just a click away instead of having to reboot) access to games requires greater discipline, in order to avoid procrastinating. :)