[littledot5566]

From my personal experiences, having a quality roommate (not in same bed) forces me to adopt a normal sleep schedule. I don't want my activities to wake my roommate up and turn his day bad, so I sleep shortly after my roommate goes to bed. But when I live alone, I procrastinate my sleep, I would rather watch videos than go to bed, it wouldn't disturb anyone anyways, and the chances of having an abnormal sleep schedule becomes the norm.

Perhaps there is some psychological/social aspects to sleeping and what you and I have described falls into this aspect.