Just because men cannot physically give birth doesn't mean it isn't their issue too. It just happens that it
always affects a women due to pregnancy and childbirth and doesn't necessarily affect a father at all, but it can. In fact, including and affecting fathers tends to improve things for women.
People in all sorts of relationships adopt or otherwise have children. Folks die during childbirth. And while men cannot physically give birth, I've met plenty that enjoy child-rearing. If it were possible with my spouse and I, I'd happily work while he stays home. (He legally has to support me due to immigration laws). My ex stayed home while I worked, though to be fair, he was on disability. I do not have children (and have no plans to), but we have discussed adoption of an non-infant/toddler child (along with their siblings if they have any). While I see plenty of reasons for one of us to take parental leave, I don't see any reason why that would absolutely have to be me instead of him.