Often enough I'm asked the perennial question, "You're not going to tell me my dog can't sleep with me, are you?" Just the way owners ask this tells you there's a problem with this behavior. If it's so expected, why do people ask? The answer is because they know it's not a good idea but need verification. I explain to owners that allowing our dogs to sleep with us on the same level and in such close quarters can lead to other problems. In building Leadership or sound "dog parent" skills, allowing dogs to control space at this level in sleeping quarters, instinctively provides the dog to feel entitled to be of equal hierarchy in our domesticated dog pack mentality. Simply put, it's a hierarchy move for our dog which allows it to feel it's on the same "level" within its pack, as its Leader.
More troublesome can be other behaviors that manifest themselves by giving Junior landscape to lounge upon. He may become territorially competitive of his position on the bed. He may react aggressively by snarling or growling when you pull the covers or move about changing your position. I've had clients report the guarding of significant others when they join their partner. Some dogs will ratchet up their warnings to snapping at a owner to defend their position. Needless to say, our relationships with our canine creatures are better served by teaching them to sleep at a lower level-upon the floor. This can be in their crate or on a dog bed. I advise owners to have them tuck-in at a place that's away from the bedroom (King's Lair).
The crying shame of the matter is the reasoning behind it all. Ask yourself or your partner, "Are you sleeping with the dog to benefit him/her or yourself?" The answer is always in the interest of the owner. Think about this, don't you want the very best for your dog? Of course, we all do! Then it shouldn't be a problem sleeping without your dog. If one continues this practice, then the fact remains: the owner is acting in self-interest only, and not for the betterment of their dog.