I have indeed thought about this, and I am currently reading your post (with an open mind) however my stance as of yet is that women choose non-STEM fields, from my observation of choices women I have seen make while growing up. We are living in an age and society where we have the most opportunity and support that there has ever been. I have never experienced, nor observed any girl being encouraged to stay away from STEM fields, and although men can be surprised when women are interested in those fields that does not mean that they don't think its right, or they are against it or even that they have been socialised to have those views. It's just uncommon for women to have those interests.
Now for those who do, I think its amazing, I applaud female mechanics and engineers, its super badass, I wish my interests and skills sets lay in those fields because that would be pretty cool.
But for me, as is the case with a lot of women, I just prefer the nurturing side, to me the idea of being a housewife, looking after my husband, raising children is utterly appealing. Not because society says so, trust me, I am the stubborn type to do the opposite of what someone suggests just to be independent, but because of my biological disposition, because of the way I was created, the maternal instinct within me. and I believe that this is the same for most women.
Could there be more encouragement of women in STEM fields? Of course and that would be great. But is society pushing us into fitting certain moulds? No I don't think so.