Maybe it's based on millions of years of biological differences in their capacities and functions (starting from body strength and role in reproduction), plus differences in social roles, of which some of the latter might be arbitrary, but some are necessary adjustments every historical society understood.

The big idea lately is to ignore all of that and just give everyone equal rights but unequal responsibilities.

I always find it really amusing that the most pro trust the science people who are in total agreement with all the evolution theories are often also the ones who are the first to be in complete denial that us humans might actually share some characteristics with our closest genetic relatives (chimpanzees).