I think that in general, people don't like to sleep alone. Mom and dad sleep in same bed a lot of times. People sleep with their dog(s) or their cat(s). People sleep with stuffed animals. It's not any different for a child. It's just my opinion, but I don't see why children have to sleep alone when everyone sleeps with someone/something when they are older, if that's what they need. Some children don't need/want to sleep with someone/something else. Some adults don't. But I think it's okay if they do.