Back around May of 2017 when the game was still in early access, I knew a guy who would fall asleep at the keyboard.
Then wake up with his character a few levels higher, but naked standing near his spawn point.
Steel was top tier armour back then, and I think he said he lost around 8 or 9 full sets by falling asleep.
At least in Elder Scrolls: Oblivion you had to put a weight on the keyboard to keep the “run” button pressed before going to sleep to gain exp. Kids these days have it way too easy.
Passive exp was a sort of bonus for surviving the lands themselves. When the game was in early access, the environment was much harsher and harder to survive in.