The female who perform a DP can be said to be a highly-evolved slut, aware that she's a sensuous, attractive being who inspires lust and is willing to give herself over over to 2 (or more) men who can use her as a tool for their own sexual gratification, while she opens up all of her body to their desires. All in her quest for a great orgasm.
Anti-porn lobbyists maintain that the men who watch DPs in pornography know that the vast majority of women outside porn don’t want it, and this knowledge is at the center of the sexual charge. It’s a social taboo: a sexual practice considered by many to be inappropriate or immoral: hence the sexual attraction of DPs.
However, in reality, double penetrations appeal to males because it is a woman totally opening herself up to male sexual desire without even the subtlest notion that this is some kind of deeper relationship. It is sex. Nasty, intense sex. Which is what truly great pornography is all about.