I think going back to OP, it's a simple answer, and it has nothing to do with math, the competitiveness, the killer instinct. It's simply numbers. Fewer women play than men (obviously). However, let's look a little more closely. The really successful women that are on the circuit are on par with the really successful male players. Why? Because they study the game, work on fixing their leaks, and play. Being female does not put you at a competitive disadvantage to men.
It's like Phil Ivey once said about Jennifer Harman. He said she's not one of the best female players in the world, she's one of the best players in the world. It was a disservice, that he pointed out and he was bang on. We can say that about Vanessa Selbst as well. She's one of the top "players" in the world, forget gender.
It's a great game to play, whether it's in a more relaxed, casual environment of a home game or a competitive venue like a casino (I'm leaving online out of this comparison). It's unfortunate that there aren't more women playing this game, but at least the ones that I've had the experience to play against, their abilities range from beginner to really good, exactly the same as the men.