I blame the patriarchy and male privilege. Sometimes men just cannot handle it when a woman appears to be *better* than him at anything. Society conditions men to be the best, the brightest, the breadwinner, the boss and there are men who relish that ideal and freak out at the thought of a woman being better than they are.
I dunno Trill - DH was brought up very patriarchical and is fine with me being better than him at various skills, including, occasionally, areas where he excels (just as I am fine with him cooking a wonderful meal, for example). Whereas my mother is NOT happy with my father being better than her at things. I think a lot of it is personality, although I will admit that men are more enabled by society to let this side of their personality show than women are.