I started playing WoW on day 7. I just canceled my account this February. I still enjoy the game, but in the last several years, I've gotten married (which affected playing time slightly), and in January had a baby - which completely killed all available playing time. I wasn't going to pay to not play a game I didn't have time for any more. Now, my games consist of facebook games, because I can play for 5,10,15 minutes and drop it and take care of the baby - not possible in WoW. Maybe when my daughter doesn't need as much attention, and I don't need to sleep every chance I get, I'll re-join, but until then, I'm one of those non-subscribers.
I suspect that I'm not the only person who's gone through several life stages over the last several years, and well, that's what happens.