because laws like this were made to offset the patriarchal dominance of a society shaped by men for centuries. it's unfair to women to let men just take those offsets away from them and it's the elephant in the room that nobody wants to address as they cheer for trans-women's rights.
I mean with the different rules based on sex/gender can cause this sort of issues, having just one retirement age for everyone for example could be easier
i'm guessing you're too young or foreign to remember what the economic landscape looked like in the 70's/80's early post civil rights era. there was rampant poverty in black communities, especially in the south where i'm from. affirmative action helped bring those people up from that (but didn't finish the job - there is still rampant generational poverty). those were good government programs aimed at a more egalitarian society. sorry if that sounds 'sketch'.