I suspect women aren't attracted to computer science careers as often as men because they generally like more artistic and creative ventures. In other words, most women prefer careers and interests that allow them to be hand-on empathetic with the objects and people around them. In general, computer science is hardly portrayed as such a career. It may involve aspects of these things, but women generally aren't aware of it. The role models they see are all in the same sort of areas, and the majority of their female peers are all into the same sort of things.

It creates something of an echo chamber that simply multiplies a compounding effect with dominant culture that discourages women from even entering a computer lab filled with sweaty nerds, much less think about joining them.