Well, apart from a time not long after I started watching when I didn't quite 'get' that Raw and Smackdown were the two main weekly shows (and even then, I wasn't always sure when they were on), I've pretty much watched regularly since mid-2001. I think it's a case of 'I watch it because that's what I've always done', like Hammy said.
I should probably watch ECW, since I often hear about how good it is. I watched like, the first two episodes and stopped after I decided that Raw and SD was enough wrestling per week.