Do people make movies of themselves because we think we're all beautiful-looking porn stars, in our own heads? As proof that we can do it?
Did do it? Or to regard ourselves, a kind of narcissistic spectacle.
There's a sense of exposure and vulnerability when fucking. Sexuality is personal, specific and impossible to describe. Only to show. And feel. A bit uncomfortable, daring, not sure how it will turn out, and so very exciting. A hope for acceptance. Success. A good time. And no embarrassment.
Vulnerabililty. So to capture that moment, that epiphany, that climax, and express it.