There are several reasons on why hitting your dog is not only unnecessary but also just plain dumb. Even so, many people admit doing so. In most cases it is used as a punishment for some action already passed, like launching on the leash or disobeying a command. Sometimes people explain hitting is necessary if the dog acts uncontrolled, to show ”who's the boss”.
Excessive submission is not ”being sorry and asking forgiveness so mommy/daddy is not mad”, it is fear. Unfortunately very many people, even after being explained that, still insist their dog is ”knowing it did wrong”, not being fearful.
Submission after being punished with physical force is not shame. It is fear, and everyone who has studied dogs and their behavior agrees. Whenever dogs correct each other with teeth, they do it WHEN the other dog is acting up, not AFTERWARDS. If dogs correct, if one can say so, afterwards, they are usually tense dogs and nervous dogs that get worked up and remain in aggressive, nervous state. Later, that nervousness erupts as aggressive behavior. We as human beings that have given ourself the right to own a dog should be above primitive stress reactions such as blindly punishing an animal from an action that has already passed. It trains the dog nothing but to fear us. They may work out of fear, true, but stop calling it training. It is violence.
Submissive behavior after being hit often includes extensive tail wagging, lowered posture and ears against the head, possible licking of face or dog's own lips and ”being friendly”. Dogs use these gestures to lower the aggression of the other part and to show they are not a threat. It has nothing to do with being sorry about misbehaving, and therefore hitting is not training. If the dog behaves afterwards, it is not because of training but because of remembering it got attacked by it's owner earlier. In many cases the dog is also getting a completely wrong message; it gets punished when it does the right thing and gets back to it's owner's reach. There is hardly any sense in that.
Not so fun fact is, only dogs that are prone to search human advice and have a will to please submit after being hit. Hard headed dogs that have no will to please often attack back or start to act aggressive and tense themselves. Many people using physical force claim their dogs ”need” that or that their dogs ”can take it”. They take it because they want to work with their owner and they are submissive enough not to fight back. Try that attitude with a strong breed, like a livestock guardian, and you'll lose an arm.
Train your dogs. Violence is a bad option when trying to build a relationship.