Gay guys don't have to work as hard. I mean, in college once a girl asked me to come back to her dorm so she could "**** my brains out", and I didn't refuse. But it rarely works the other way around, unless you're a celebrity and/or rich.
I think it's biological, women have far more to lose than men from a casual sexual encounter. Like 9 months of prergnancy followed by 18 years of trying to get child support payments. Birth control is not failproof.
I disagree as I think it is entirely a social construct these days. Now it may be that there were good (in the sense of pragmatic) reasons why our societies developed the stupidity and hypocrisy in regards to sex that we are left with today but they no longer exist. That's why I think a better change to work towards would be changing the stupidity and hypocrisy rather than trying to re-enforce it.