I wanted to say something brief about why I think female tech role models matter because when I was younger, they didn't feel important for me, regardless of whether they were subconsciously. I'm really lucky that I currently work somewhere where my gender feels like a non-issue, thanks to a combination of fab colleagues and the general ethos of the OU. But somewhere along the way, I learned what it felt like for that not to be the case.
This is difficult to discuss of course - it is hard to separate who you are from your gender and it's always far too tempting to extrapolate from your own experience to that of half the population. There is also the danger of slipping into criticism rather than taking positive action. I do think it's important however that there are more female developers - not just because seeing lost talent is saddening, but because being a developer gives you power to shape technology. We need female developers if we want to avoid unintentional biases in the technology that we use in our lives.
The critical thing is that the type of behaviour that is effective for men is different from that for women. For a start, people, often don't react to the same behaviour from men and women in the same way (see e.g. here or here). But it's also a bit more complicated than that too. From an anthropological viewpoint, all-male, mixed and all-female groups behave very differently. When you're the only woman in a large group of men, the men you are with are still in 'all-male' mode but there is no socially established way to act in that type of context as a woman. You are pretty much by yourself trying to figure how to fit in without losing your femininity, as well as things like how to stay sane when you don't talk to anybody all day (not all programming jobs are like that though, phew). On top of all that you have to resist succumbing to the psychological phenomenon of stereotype vulnerability. The net result is that watching how men behave doesn't always help you figure out how to behave as a woman.
Modelling other people is an important way of learning how to improve at things. So if you are a woman, it makes a big difference to have women rather than men whose behaviour you can model. One way to think of it is this: if you played a hunter in World of Warcraft, you'd learn a lot more by watching a great hunter play than by watching a great mage. Gender in real life is similiar in some ways to the notion of a class in World of Warcraft. You can both achieve the same things, but because of cultural differences (that nobody has really figured out how to change yet), you might get there more easily by going about it in slightly different ways.
Of course there are other psychological factors such as this study describes related to why women get so much more inspired by other women than by men, that as far as I know we don't quite understand yet. But as a note to my twenty-year old self, the reasons above are why I now think female role models in technology are so important.