As you say, these works are erotic fiction. Their whole purpose is to be titillating, so naturally, they have sex scenes.
I don't see how this refutes my claim that sex scenes exist for titillation. The plot of Lady Chatterly's Lover (ie, the drama of her affair, her crumbling marriage and the resultant scandal), does not progress during the sex scenes. The consequences of her affair will still occur, even if you, the reader, are not privy to every graphic detail of her sexual encounters.
I don't think you understand D.H. Lawrence well if you would argue he would want the book to be shorn of the "sex scenes". After all, the book faced an Obscenity Trial, and several other authors came to his and its defense. Lawrence could have easily removed the more "scandalous" passages, but refused to. I think if you examine his driving literary passions, you might see why.
The book is about far more about sex scenes, it's even about deeper themes than the story of an affair, such as a changing society ... but having read the book, and knowing the author, I do not think HE would agree with you that the book would serve the same purposes without those scenes.
At the end of the day, writing is (or can be) a very sensual medium. By that, I mean a writer can evoke the feeling of a warm sunbeam on your skin, the feeling of a dipping into a cool spring on a hot day, or the moist sensuous feeling in your mouth of consuming a madeleine cake. Is that "titillation"? And if so, why shouldn't they do it?
Only when what they chose to evoke are feelings of an erotic nature, do people now somehow say that serves no purpose. I would say for D.H. Lawrence it served a definite purpose, of curing and counteracting a mind and body being divided from each other in an industrial civilization.
We're far away from the interesting questions of whether a video game can do a sex scene right - and it's possible that with the current goals for most video game writers as well as the tools available to them and the audiences they have to satisfy, most here are right that the answer is "no" - but no, I'm sorry, I will not agree that you could remove the sex scenes from Lawrence's novel, and still have the same book.
I happen to believe that literature can get sex scenes right, the problem right now is most game authors - and yes, alas, perhaps Bioware as well - are not trying hard enough to write games worthy of being called literature or art. And that is the larger meta-problem.