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.
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).
The big idea lately is to ignore all of that and just give everyone equal rights but unequal responsibilities.
If strength is relevant, should particularly weak boys be "treated like girls"?
Should particularly strong girls be "treated like boys"?
Should girls and women without functioning reproductive systems be treated like boys?
What differences in social roles have been proven "necessary"?
Is the fact that chimpanzees do things a certain way remotely good evidence that we should do something that way too?
Answer key:
- no
- no
- no
- which gamete you supply?
- no