Well, for one thing Computer Science went from being a largely theoretical, mathematical field, to being more about useful programming and system architecture. When people make arguments like the one you are making, you completely ignore that the CS field is constantly going through giant paradigm shifts. It is completely unfair to compare interest of the various genders/sexes from 30 years ago because the field is completely different.
This isn't proof as it is entirely anecdotal, but I have a lot of women friends who love hard math and absolutely hate practical programming problems, while the majority of my guy friends fall on the other side of that divide. That is only one possible explanation.