Another way to look at it could be, "Why aren't more women interested in trading?"
It's been a long, long while since I've attended one, but if you go to those free trading conferences you'll see that there are significantly more men that women who go to learn something about trading or to get started. These days, I'm sure it's likely a more balanced attendance, but I'm also guessing that it's a high probability there's still more men than women.
Until you get the same number of women interested in trading as the number of men who give it a shot, it's likely that number will be skewed.
Well, that's my two pips.