system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we like to sleep with a hand under our head?

Hands are harder and less comfortable than pillows, so why can't I sleep without my hand supporting my head?
gpt
Perhaps it's a natural instinct dating back to when humans roamed the earth and didn't have luxuries such as beds and pillows. While a pillow is softer than a hand, a hand is softer than rocks and cold ground.