It shows a lot of semen, especially in gay porn. The climax is the best feeling, it is riding off your orgasm, the most awaited part of sex, the final ending everyone is trying to achieve.
It does not even matter what gender or race you are-you come and resort to porn in order to, well, cum. If there is a common goal in every porn, it is that they all want to achieve that sweet blissful orgasm.
