I'm not anti-Linux by any means but, in my case, I just don't want the hassle. Windows, mostly, works. Once all the "superior user experience" has been turned off - my XP looks like Win98 etc - it just sits there looking after mouse and keyboard.
Ok, not a good reason but it's handy from the PoV of knowing how to fix other Windows PCs and it means I have an absolute menagerie of (mostly free) s/w at my fingertips. To me a computer is just a tool to achieve something and I do many and varied somethings. While Linux no doubt has a great archive of stuff, I don't think I could be bothered to run a dual boot system for the times I can't find something.
I'm indifferent about using Macs for the same reason.