There are several reasons for this. One, is I've been so busy that it's hard to find time to breathe, much less throw precious moments of my life down a timesink. Second, is the last few times I played, I didn't exactly have a good time, either. Third, is that, well, even good MMOs still suck. 
Also, I'm sort of wary of what I may find if I sign back in. I'm sure the rest of my kinship has hit 50th+ level by now. I don't know what if any changes there have been made since I played last either, so I'll have to get re-used to playing my character again (which I'm not real keen on) or start a new one (which I'm definitely not keen on).
On the other hand, I'm pretty darn stressed and could use some gaming right about now. If only Neverwinter Nights 2 didn't also suck, I could play that.
 Note to anyone who likes MMOs: I'm glad you enjoy them, and by all means continue to do so. But just like I will never like fried okra, you're not going to convince me that MMOs don't suck. Play them and have fun, and write me off as a lost cause.