That's a very interesting thought, Mattie. So, to you, marriage is about one partner saying "do not touch her, she belongs to me"?
From my view, each person in a relationship should be saying that for herself or himself. For example, in my relationship, I do not need Bob to say to anyone "she belongs to me". I am the one responsible for saying "I am not interested". I do not feel I should ever have to rely on having Bob "threaten" guys away from me.
Otherwise, what would happen if I was in a club, and Bob wasn't there?