I wrote a novel that got poor reviews (among the two people who read it). Many of them (all two) mentioned that there was "too much sex."
Now, I wasn't seeking to write an erotic thriller or anything. But I also think that sometimes sex is necessary to tell a story about the human condition (a condition which involves sex), and that there's a difference between sex with meaning and meaningless sex.
Take, for instance, Submission, by Michel Houellebecq. (NOTE: Before we go any further, I am NOT saying, "I wrote a novel which can be compared to a novel that may well end up being one of the classics of our time." Let's just be clear on that. I wrote a novel that was begun by five readers and finished by two, and which was unliked by either of its two completers.) Now, I wouldn't say Submission features a lot of anal sex, but I feel most readers would agree that anal sex is like sriracha sauce: a little goes a long way.
Couldn't Houellebecq have written the novel without any anal sex? I say no, not really. Because the anal sex is an important figure for the total submission that the narrator wants from his sexual partners, which in turn is an important figure for the total submission that the Islamic rulers of France want from the narrator. Submission doesn't contain anal sex because Houellebecq is a perv; it contains it because he's trying to say something about the relationship between European non-Muslims and Islam.
Maybe I don't do a good job saying what I mean to say. That's very likely. But it's also possible that the sex is there for a reason, and if our reaction is to say, "Eww, sex! Skip it!" we will be missing the reason.