For starters, no one is saying it's pg's job. The interviewer asked him if he felt there was anything he could be doing to get more women into YC.
Second, "encourage" does not mean "order someone to do something." No one is going to up women, putting their hands on their shoulders, shaking them, and telling them they must be developers! Instead, they're creating spaces that are welcoming and friendly to women. They aren't forcing them through the door; they're opening it for them and showing them all the delicious cookies inside.
Yes. There are plenty of initiatives to get more men into nursing, fashion, and teaching. Just because you didn't take the three seconds to search for them doesn't mean they don't exist. You don't hear about them because, what a shocker, you aren't part of those communities. It's almost like you're on a website dedicated to tech culture or something!
If a service was allowed to say that they had 0 requests, perhaps more users would flock to that service as a less surveilled alternative to a competitor that is in the 1-249 bracket(or higher).