They’ve had the physical stuff covered for a long time, but imagine the socially and emotionally charged atmosphere that must come with having to film something personal and intimate with a coworker. Both actors might have spouses at home, maybe they’re super close friends off camera, maybe they’re playing a different sexual orientation than their own. Who knows. People are messy. Everyone thinks about sex a little differently, so when you add all these things into a work environment, having a third party there whose job it is to prepare the actors and crew for exactly what’s going to happen when the camera is rolling, keeps things professional and makes sure each actor’s wishes are respected. Seems like a win for everybody.

If it makes everyone involved more comfortable, they’ll probably do a better job at making whatever tv show or movie they’re on, and it will be more entertaining for us. Plus, we as viewers can be relatively confident that none of the actors did anything they didn’t want to do.