Like dogs, humans in some ways, are pack animals too. But we all learn to sleep alone in our beds, rather than with our parents or siblings, without feeling lonely or worrying that they don’t like us.
We know we’ll see our family and friends when we wake up the next day. The dog has drawn the same conclusions, and may even feel that his preferred sleeping spot puts him “on guard” to protect the family.
The assumed health risks of having the dog in the bedroom are probably overstated — if you’re taking good care of the dog, living with it may actually be less likely to make you sick than living with your human family, since many diseases are not likely to cross from one species to another.
There is some risk of fleas or other parasites crossing over, depending on what your dog is exposed to, but I’m not convinced that’s much greater if the dog is sleeping with you than if he isn’t.
However, the simple fact is that many adults really aren’t comfortable with having animals sleep with their kids, and as long as it’s their house they get to make the rules. If a child wants this, of course when you’re living on your own, you’ll be able to make your own decision.
This is speculation, but there may actually be some minor psychological benefits to the dog in not sleeping with you. Dogs are much happier when they know exactly what their status in the pack is — who they are and aren’t dominant over.
Where they get to sleep shouldn’t confuse that, but each rule that they have to follow and ones that you don’t, helps them realize that you’re allowed to boss them around, not the reverse.
Dogs sleep where they’re allowed to sleep, just like you don’t usually get to sleep in the living room or on the kitchen table even if you want to. Some people do let the dog sleep in the same room with them, though usually not in their bed.
Some people believe that “animals belong outside” and insist that dogs should sleep in a doghouse even if they can come into the house during the day.
Some dogs sleep snuggled up next to their owners in bed. Others have dog beds (a cushion on the floor), some sleep in their travel crates (this is becoming more common), some dogs curl up in a spot that’s warm and not drafty, others (as I suggested above) pick a place where they can watch out for unexpected visitors.
There really is no definite answer. It really depends on the person and temperament, and other factors of the individual dog.