I get that people might disagree with this, but I think it really comes down to how long they've been playing the game. I don't have any data to back this up, but I would assume that if you polled most VCT pros, they started playing fps games at a very young age. I'd also be willing to be that if you did the same polling to GC teams, the average age you get would be a lot higher, probably around early teens.
It's a well understood fact of psychology that skills are way easier to learn when you're younger. I.e., learning a language or an instrument is a lot easier when you're a kid then when youre in your mid twenties. People that have been playing since they were a kid develop the essential habits way quicker then someone who decides to start playing later in life.
As for why this is the case, you can look at the score eSports channel and look at any story of pro players. They tend to have some sort of older brother, friend, or father that gets them into gaming at a young age. It's true that in society, we tend to discourage women from gaming when they're young as we don't typically associate it with them. I can only speak from anecdotes, but my female friends who got into gaming only got into it because of friends they met later on in their lives.