I can fall asleep anywhere and just about any time. Thank the Lord I can fall asleep during prayer now, this might save me from Hell. No wait... I don't believe in God I guess this doesn't help. On the other hand it helps make flying tolerable if you can fall asleep before take off.
Have you ever been to a Catholic service, a lot people are falling asleep. How long can you hold your head down with your eyes closed while some old man drones on and on, the problem comes when you snore.
Snore once at church and all of a sudden your girlfriend doesn't want to take you to church anymore.
Good thing airlines don't care, and I don't care if the other passengers do so it works out.