Becausse of various things, but mostly because I can sleep for insane ammounts of time. If I have the time and the means, i sleep between 12 and 15 hours a day. And it's not just "oh I'm tired, i'll take a snooze" it's a dead sleep, like i've been deprived for weeks and nothing but the world exploding can wake me from.
But then it flips, and if I want/need to, I can stay up for days.