The thing is, for any org to sign a woman to their main roster, this woman would have to be significantly better than the available men. Players like florescent or Mary are definitely mechanically at the same level as any Tier 1 pro.
The reason they're so far behind is that they're lacking the experience, and the reason they lack the experience is that they're so far behind. Signing a GC player to a T1 (or even T2) team is a big risk which for orgs just isn't worth it.
And on the other hand for GC players it's of course also a big risk to sign with a T1/T2 org because in GC of course they have much higher job security. This is why GC is here for the development of the scene and the long term goal is to get rid of it eventually.
There's not really any good reason to assume a biological component, because many of these effects also exist in other parts of society. I'm a bit hesitant to name examples because it often involves sensitive issues. But given the current state of research, it can pretty safely be assumed that it's purely social/cultural.