Increased obesity is definitely part of why straight men reject straight women. Mental health is probably the number one reason why straight women reject straight men.
straight women expect straight men to be willing to go to therapy, but also to not need it in the first place
the mental health expectations placed on straight men are unrealistic
meanwhile, gay men see traumatized men and try to claim them. There’s a misunderstanding that men who got picked on in school are ripe for gay conversion.
Not all gay men are predators, but hey I’ve been sexually harassed by both straight women and gay men, and it’s definitely more gay men.
I think it comes down to how the different groups perceive mental health difference, and perhaps that gay men feel safer pushing when they’ve already gotten a “no” versus straight women who have more to worry about regarding their safety.