Here's a recent article about it:
http://www.bbc.com/news/business-39579321
In the west, the woman is traditionally the housewife.
Hence, a smart woman wanting high social status kind of had two options: become an engineer or a doctor. First option was easier and also less painful (doctors were also subjected to nasty shit like having to relocate to unpleasant places without choice because there was a demand for their services there, some areas like surgery were also much less women friendly etc.).
Also, dunno about Rusia, but in Eastern Europe, even now, there is a good "girls in math" story. Maybe less in physics or computer-science, but in pure and applied math there's lots of girls. Probably most of the smart ones jump ship more towards finance than tech though, when they realize they can't really get a nice paying job with a math degree alone.
The thing is - positive discrimination doesn't solve the problem, because it comes from school. You need to encourage girls to take science classes - it has to be expected of them that they do so (rather than go towards, e.g., humanities). That, I don't think is actively happening in the US or even some parts of western europe.... by the time you're dealing with graduates, it's already too late to fix the gender-imbalance problem.
[1] My little daughter's godfathers are German (she grew up in Romania, but he didn't). She told me that among german women, it's a thing of pride to be bad at math. And that her daughter was praised in school that "you're pretty good, for a girl". With that sort of attitudes during childhood... it's bound to be hard to get gender balance later (that "praise" would be perceived as insult here)
When I was going to school girls were usually better at math. I remember getting help from them with some calculus problems.
My CS teacher in high school was a woman as well and before teaching she worked as a programmer. She was a great role model for girls I'd imagine. Well she was a great role model for me too because she was a great teacher.
Not being familiar enough with history of this in US/Silicon Valley, want to ask: were things always "unequal", or did things go wrong somewhere along the way?
So yes, it makes sense to have a movement for diversity here, because something is pushing women out of these fields, so we have to push back.
I'm not sure for the increased participation of women in tech though. Maybe better education? Maybe less of a "computer lovers are all nerds" culture? I honestly don't know.