I can fall asleep almost anywhere. I routinely fall asleep in the break room at work. Once, I was helping a friend fix his car, and I fell asleep on his garage floor when he went inside to get water.
But in a hot metal tube tearing through the sky, with my neck all kinked? Get out of here, man.
Then you start snoring and people wake you up anyway.
My last flight had a massive snorer. It was pretty funny at first. At hour 8 it was insanely frustrating. He was woken up four times by various people. Went straight back to snoring.