That's a good question with a pretty deep answer, that I'll try to keep minimized. Evil isn't something I get to explore very often, the times I have had the chance have been the most immersing games I've ever played. It keeps you on your toes, I like knowing that that breath my character just took could very well be his last even in company of those whom he might travel with. It's the danger thing, really and having the freedom to do whatever I might want to do and how I want to do it. It's true that you can do that in some good aligned campaigns, but I've had too many DMs disagree with my outlook on alignment for my good characters to really come out into the light for what they really are.