Another off-shoot of this behavior is the 'sandwich' where Boxer dogs will sit on each other but also on their human. The owner is sitting on the sofa, 2 Boxers will come up, 1 on each side and squish, wiggle and press against him, essentially sandwiching him in place. Everyone in place? Okay, you watch TV while we rest in this very comfortable way!
They have no clue that their human may not want to be wedged into place. He/she is part of the pack too! (And hopefully if you're training your dog correctly, he/she knows that the human IS at the top of the pack).
Some people worry that when a dog sits on an owner it means that the dog is displaying dominance over his human. This is rarely the case when a Boxer has been trained properly. Think of it this way, if you had a small dog such as a Pomeranian or Chihuahua and the dog came over to your sofa and plopped on your lap, you would think nothing of it.
Well, the Boxer will do the same thing - his need for closeness and wanting to next to you does not depend on his physical size.
When a dog feel relaxed and comfortable with his human pack leader, he wants to be included, he wants to be in close proximity and yes, he'll want to sit right up on you, even if he is a 50 to 70 pound (22 to 31 kg) dog.
The only time that this would be an issue is if a Boxer dog attempts to sit on a young child that is small enough to be harmed or smothered by this action.
When you consider the pack and leadership ranking in a household with both children and dogs, things can become a bit tricky. Is the dog a sibling of the child? (Same ranking in the pack) or is the child to be considered a leader (Alpha to the dog)?