GreenTongue:
I suppose saying nothing is less DRAMA then trying to explain?
I've had a few frank conversations with other players/GMs over the years and there's a bit more to it than that. Some people feel a certain anxiety that comes with being a GM and feeling like you have to post. When you can't post, you find that you can't face the pressure of posting, so you don't post... which means the next time you should post, you feel even more pressure and even more don't post. It leads to a weird avoidance thing that results in you vanishing.
I've not done any really deep psychological study of it or anything, but it's kind of like how people with OCD cleanliness issues are the ones most likely to end up on Hoarders (or whatever knockoff is still on the air). When things build up, you don't know where to start, so... you just don't.
I have some of that to me, so I make it a point to communicate about my absences, plans, schedule, etc. My entire posting for a week might be explaining why I haven't posted, but that's better, in the long run, than just not posting. I can totally recover from a week like that. I can't necessarily recover from missing two weeks and then having to catch up.