Sex shouldn't be hidden from an adult audience. If they cannot talk about sexual issue, then sex once again becomes something oblique, shameful, and clandestine. If they are only sexual in private, then they will be encouraged to be silent about sexual issues they may face. If people aren't sexual in movies, then they are only sexual in private.
Removing sex from movies is, in a vital way, removing it from everyday conversation. It also feeds into a widespread fear of sex and sexuality that has been deeply infecting an increasingly conservative discourse at large. And while leaving most characters' sexualities abstract might provide a broader canvas for writers of slash fiction, it is, in many ways, a form of censorship. Audiences have reached a point that mainstream cinematic entertainments are largely sexless, and any tiny crumb of sexuality is savored.
So while it may be understandable why audiences weaned on fantasy violence may expect sex to be deliberately removed from their preferred stories, in doing so, many vital elements of the human condition are being deliberately excised.
