Probably because most of the men think they have to work to make money. So they choose to work. While their women prefer to take care of the household rather than work.
I dont think this is the reason why male is dominating the use of bitcoin. We are already in millenium times. All the things the male can do can be done by female too. I think the reason why there are more male in bitcoin is because male has more interest in this line of job. And males are more dedicated when it comes to computer related works.