Disclaimer: fuzzy brain; struggling with words today.
It's more than 'vested interest,' I think. It's less consciously motivated than that.
What I mean is, if you imagine your DD starting from birth, you have no idea whether she's infertile, whether she'll be prone to miscarriage, whether she'll be a lesbian, whether she'll be raped, whether she'll end up pregnant at wanting not to be ... etc.
But you and the society around you will raise her in the understanding that she has a womb and that these things are included in the range of possibilities for her.
If you have a DS, you have no idea if he's infertile, or gay, or will be raped, but you know he will never miscarry, he'll never have an abortion, and he'll never be pregnant. So you know, and society knows, that his experiences will be different - he might have a wife who miscarries or a girlfriend who has an abortion, but you know and you expect he won't experience it himself.
That whole context is what makes some things 'women's issues'. Not the 'vested interest' we develop when our lives take a particular turn. I think 'vested interest' issues are more like, oh, the fact that I care about funding for theatre because I like plays, or something.