i believe part of the reason could be that men tend to be more aggressive and women tend to be suppressed. there is also the notion that tech in general is a man's field and also safe spaces for women in the blockchain world have not been created. also there needs to be more role models so that other women can aspire to be like them.
I think that most of the womans does not really focus on bitcoins and they think of cryptocurrency as a pyramid scheme, in this way not that much woman will get interested and focus on other things. There is also a chance that most of the womans are focusing on taking care of their children and that is the reason why there are more men who are having a business related to bitcoins.