Sex in marriage should be one of the greatest expressions of love. It's power goes far beyond stimulating the senses. Sex, or more appropriately, making love, unites husband and wife both physically and spiritually.
You can call it testosterone, chauvinism or whatever you'd like, but the reality is that men long to be the hero to the women in their life. Without an outlet for this natural urge a man will become dissatisfied. This dissatisfaction may express itself in a variety of ways, all of which can hurt a relationship.