I think it's the individual child's (intrinsic and extrinsic) motivations. Case in-point, my eldest daughter (14) is a studious introvert with a strong mastery

I think it's the individual child's (intrinsic and extrinsic) motivations. Case in-point, my eldest daughter (14) is a studious introvert with a strong mastery of Latin and formal logic but loves beauty and wants to be a hairdresser (meh) or Instagram model (barf). Programming and robotics just don't do it for her even though I'm certain she could be good at it. My middle daughter is wicked smart extrovert with zero patience an excess of confidence and absolutely loves robotics, electronics, Goldiblocks, etc... I'd hate to work with her on a software project because she's so agressive but chances are she'll wind up in STEM. So that takes care of intrinisic motivation, as for extrinsic, both thought programming was something only nerdy anti-social boys do. In fact boys and girls chastised my middle daughter for liking so called "boy" things like building a trebuchet or going to the comic book store. If we assume that only a small percentage of children will have both proclivity and potential and that we then also have to play peer-pressure Russian-roulette until they get to college then it's no wonder so few girls are still getting into STEM.