"In my experience and that of people I talk to — and in the vast majority of porn — it seems commonly accepted that sexual activity ends with a man’s orgasm, whereas women are commonly expected to continue engaging in sex after having an orgasm … despite the fact that many women seem just as tired and less-interested in sex post-orgasm as many men are. In part, this goes back to defining sex in terms of reproduction: men have to orgasm in order for reproduction to happen, so men’s orgasms must (supposedly) be central to sex. It’s all influenced by these other constructions, like how penis-in-vagina sex is “real” sex, or “home base”: many people are confused by the idea that you’d shift sexual gears to (for example) manual stimulation if you’ve already “made it to home base”. But it also arises from centering stereotypical men’s desires — from a culture that just generally sees them as more important, more driving, and more necessary than women’s."