Confusing Things I Didn't Notice Until Somebody Else Mentioned It

Why does Cosmo, a magazine aimed at women, have its' cover stories all about how to please a man in bed, and positions men enjoy, instead of sex tips aimed at well, women, the nominal audience of the magazine?

And why didn't I think of this until somebody else mentioned it? Because that's what patriarchy is, it's not just a matter of evil stomping boots, it's making things invisible too.