Competition with women is almost always a net loss of honor for a man. Men don't consider competition between men and women to be "apples to apples." I don't think women do either... What does a man have to gain? He shows no courage by entering the ring with a woman. He is expected to win. If he does, his victory is shallow and unsavory. He gains no honor in beating a woman- the idea is offensive even to a modern man's vestigial sense of chivalry.