Because men are risk taker, and women are quiet hesitant to take the risk for some good reason. 21% of women attendees is not that bad, it will increase soon since they are more active now compare before and the society are more open now for the women, there is nothing to worry about this women are still strong compare to other men and they can also take the risk, if they fully understand this market.
Agree to you:) well,its because some of men are doubtful if their wives attending event especially if that event most people are there is men...but on my own experience nowadays more women are open for the opportunities like cryptocurrency, it's we called worked from home.. Women are so ideal people than men..