I think it is because I think most of them are cowards.
edit: Maybe this needs more of an explanation. Men have more testosterone so they get more aggressive. Aggression is often seen as bravery, but I think it is the opposite. It's an altered state of consciousness to avoid mental stress. Even fighting and getting your ass kicked can avoid mental stress because of the pain, (ie endorphins).
Anyway... men are very often allowed to get away with owning up to their emotional conflicts as kids simply by becoming aggressive. And this carries over as they grow up. That's why I think men are a lot more often cowards than women.
anyway... that's what I did when I was a kid. I like to think that I grew out of it.... which is not allowing my life to be ruled by fear. Fear of what others will think. Obviously I feel fear all the time. I just try to control it best I can.