Mainly gaming. It is ridiculous to tell someone to go and spend MORE money on a seperate machine to game on, when there current machine works just fine. I would definetly be pissed if I had to use a Mac, and because of that ALSO had to go and spend hundreds on an XBOX360. Not to mention console gaming is not something I enjoy, I like the user ability with PC gaming to go and edit my games, make my own levels, use cheats, etc.
You'll also find people (like myself) "grew up" with Windows. We are used to it and we like it. If you are trying to tell me that Windows is a huge security risk and it has a million holes and bla bla bla, etc. Well that's nice, to datte I've never had a problem with that. I keep my computer secure and I leave it running 24/7, I game online and frequently transfer files/data across the internet using IM clients and P2P programs. No viruses or trojans or secuirty risks yet.
Alot of people like Mac due to ease of use and user friendly GUI. Well maybe I'm a super genius...but Windows is easy enough for me to use. In fact I'm quite familiar with it, switching to a Mac interface would be "difficult" for me, I'd have to re-learn alot of things and break old habits.
Mac's also sport great security and supposedly a bullet proof OS. But that doesn't appeal to me. Why? Well, as I said ealier, my Windows machine runs great, no viruses or trojans, I'm not constantly having to fight off hackers etc. And all I have running is a free AV program, nothing else.
Maybe if my Windows machine was difficult to use, or it had loads of viruses and malware issues...maybe then I'd consider a Mac. But it runs great, it has no malware issues, so the incentive to switch to Mac is...nothing really.