Because women are always overly concerned about living comfortably and being taken care of. They usually look for the path of least resistance. Marry the richest guy they can, live the most comfortable life. Follow the path that is going to secure them the most.
Lets be honest, it's men that did the dangerous exploring work, pushing the limit to the dangerous depths of the oceans, risking their lives to go to space. Sometimes men get it wrong and die, or do it for the wrong or misguided or dumb cause though. But often men are willing to risk their lives for the village. Women as a whole don't take risks. And especially in general wouldn't risk their lives for the greater good. They care to much about personal self preservation. Unless it's their child which they see as an extension of themselves. (yes there are a few brave women but in general it's a tiny tiny percentage).