That's a very modern idea though. Before the 60's, porn and pissing in public were both seen as public indecency. Equating books/movies where sex happens to pornography is silly. The purpose of porn is to arouse sexual feelings, not communicate anything, unlike a novel or a movie where a sex scene happens. Even "sexual" paintings like the Rape of the Sabines has for purpose to communicate history, not make the viewer horny.
Pornography is a creative work, but it is the same as other vice industries like alcohol. It doesn't mean to produce goods/thoughts, only to exploit emotions.