To be honest, whilst I don't want to take anything away from the author's story, and I accept that different social expectations would've played a big part, I'd suspect that the main difference was because of gaming culture.

Perhaps some have forgotten, but the gateway drug for many people getting into computers was games, especially in the 80s. Gaming culture at the time was heavily skewed towards boys and young men. I'm sure there were plenty of girls and women who played games too, but on average it seemed to be more of a male activity. Current gaming culture is much more diverse, so don't get things twisted, I'm talking about how things were back then. I think if you can explain the major influences on the gamer diversity landscape back then you can mostly explain the computing diversity landscape right now.