Some people do fall out of bed.
Throughout his childhood and adolescence, my son was one of them – whenever we went on vacation and he slept in hotel beds. His problem was that his bed at home was up against the wall, and apparently he was accustomed to leaning on the wall when he was asleep. When he had to sleep in a bed that was not up against a wall, he would fall out of it multiple times every night.
When he went to college, his bed in his first dorm room was not against a wall. I never asked him whether he fell out of it, but I was very glad to see that it wasn’t lofted or bunked.