We also don't hear anyone clamouring for quotas in higher education either (probably because it's majority women).
So, when do you think discrimination on the basis of sex is legitimate?
Personally, I can see at least two areas:
1. If a father must choose between sending his son or daughter to school due to lack of funds (as may happen in some poorer countries in the world), I think it would make sense, all other factors being equal, to prioritize the daughter on the grounds that the daughter may some day become a mother and a mother is the first educator of the next generation. If the mother is educated, she can ensure that all of her children will be too. The reason why the mother is the first educator of the next generation is that the father can't breastfeed even if he wanted to. So if anyone must stay home to care for the kids, it will be the mother before the father in most cases. Therefore the mother is the most likely educator of the next generation. Ensuring that the mother can read also ensures that she can read the doctor's prescription for the children, etc. Furthermore, since a man is usually physically stronger than a woman, in the worst case scenario, he might still be able to engage in manual labour more easily than a woman could, so giving her more educational opportunity could compensate for physical weakness in the labour market.
2. For the first five years of a child's life, it makes sense to let the mother stay at home and let the father go to work. The reason for this is that a father can't breastfeed whereas a mother can. Need I elaborate on that?
The above are about the only two areas that come to my mind where it does in fact make logical sense to discriminate in favour of women over men. Beyond that, I can't see any argument for it. And as for point one above, that does not even apply to wealthier societies since in such societies, everyone gets a chance to receive a basic education anyway. As for point two above, I suppose there may be cases when it would make more sense for the wife to return to work and the husband to stay at home, but given his inability to breastfeed, those cases would certainly be the exception and not the rule.
3. Now that I think about it, I suppose one could make a case for a man giving a woman a dowry. If the mother dies while pregnant, well, the father loses his family and that's tragic. If the father dies while the mother is pregnant or just gave birth, she's now left having to care for the child all alone. Sure a dowry provides minimal help, but it's still better than nothing.
4. Conscripting men only makes sense too mainly due to their greater physical strength, while accepting women as volunteers if they wish to join.
Where else do you think discrimination in favour of women makes sense besides the four points above?