It's Mother Nature at work to keep the species alive. Natural birth rates are skewed towards males (not taking into account cultural "interventions "). Somewhere around 52-56% male, 44-48% female. Women traditionally not only had to run the gauntlet of diseases but also childbirth which would initially make you think that Mother Nature has it backwards. However, men have a natural propensity to do stupid things and wage war, which historically has brought the number of males below that of females.
But it goes further than that. The reproductive capacity of our species is almost entirely female driven. So as long as there are willing females and a few men willing "to service" them mankind will go on. The other way around and we would likely go extinct. (Think of the cattle rancher having 1 bull to service his 15-20 cows).
So once Mother Nature figured out that men will breed just about anything, there was no need to coddle us. Thus why we have , a brain that makes us do stupid ****, propensity to beat the **** out of each other and a less robust immune system than women.