Two weeks ago, “Game of Thrones” did something very unusual: It showed two characters having a sex scene.

OK, characters on the notoriously adults-only HBO fantasy series getting naked together is fairly common. What made this moment different is that the two characters — the ex-slave translator Missandei (Nathalie Emmanuel) and the Unsullied warrior Grey Worm (Jacob Anderson) — got naked for a round of pleasant, loving, consensual sex.

For a series that has been criticized for its many rape scenes, and for casting many women in subservient roles — prostitutes, maids, serving wenches and so on — this romantic pairing was a cause for celebration.

It also raises an intriguing question: When is the last time you saw that kind of lovemaking in a Hollywood movie?

Scanning back at the major releases so far in 2017, you’d be hard pressed to find a scene with two adult actors coupling in a mature, caring way. The closest you can find would be Christian and Anastasia in the less kinky moments of “Fifty Shades Darker,” the sequel to “Fifty Shades of Grey” — not exactly role models for a loving relationship.

What happened to the great American cinematic sex scene? There are many reasons your favorite stars don’t get as down and dirty very often.

Economics drives a lot of it. A nude scene — anything where you might see a woman’s breasts and a backside or two — will automatically earn an R rating from the Motion Picture Association of America. Studios know that R-rated movies, with rare exceptions, make much less money than PG-13 films, so as long as the movie’s other elements (language, violence, drug use) aren’t worthy of an R, the suits will opt for the tamer version.

Some actors — particularly women actors — decline to do nude scenes, and stipulate as much in their contracts. Reasons for this include personal modesty, body issues (even movie stars have them) or fighting against sexism, since it’s almost always the women who are asked to bare all.

For some, staying robed is all about the internet, where nude scenes are taken out of context and filed forever on sites like Mr. Skin. Take the case of Jodie Whittaker: After it was announced last month that she would take over as The Doctor on the BBC’s “Doctor Who,” the skeevier British papers dug out decade-old images of Whittaker’s nude scenes from her earlier roles. Peter Capaldi, the silver-haired Scotsman who preceded Whittaker in the role, didn’t have that problem.

For moviegoers looking for mature handling of sexuality, often the foreign and independent films are the only option. In the past few months, movies like “Lady Macbeth,” “The Exception” and “Band Aid” have used sex scenes to explore the bonds and the cracks of their characters’ relationships.

To Hollywood, though, sex is increasingly becoming a big joke. One of the oddest trends in Hollywood this summer has been the raunchy R-rated comedy — titles like “CHiPs,” “Snatched,” “Baywatch,” “Rough Night,” “The House” and “Girls Trip.” The trend may not last long, since only one of these titles, “Girls Trip,” was a box-office success.

In these films, sexuality is the punchline, nudity a gross-out gag. But the actual lovemaking is treated much the same as in a PG-13 movie: A couple start kissing passionately, the camera pans up to the headboard, then cross-fades to the next day and someone saying, “Good morning, sleepyhead” (or something similar).

Granted, some viewers think that’s too much sex in the movies as it is. These may be the same people who nod in agreement when they see the “Cosmopolitan magazine contains porn” billboards on the freeway, silently endorsing a campaign that equates sex-positive advice articles with hardcore pornography.

With children, and the entertainment they watch, of course they should be protected from seeing what’s inappropriate for them. But when we’re talking about young adults — people old enough to get into an R-rated movie, and already forming their views of what sexual relationships are like — keeping the blinders on isn’t healthy or helpful.