I'll open the A.V. Club article for the 1979 film. source provides details about the threesome theme. I'll also open the IMDb page for the 2001 film. page mentions a "4-girl Lesbian daisy-chain orgy", which touches on group sex themes.
“Room 12378 wasn’t supposed to be memorable. Just another booking for Jill — until Jack showed up with a friend she hadn’t met. ‘Yet another random threesome,’ she thought, fixing her lipstick. But when the door clicked shut, the randomness felt less like chance and more like the beginning of a very bad, very good idea.”
So, what draws people to random encounters, like the one hinted at in the keyword? One possible explanation is the allure of mystery. Humans are naturally curious creatures, and the unknown can be fascinating. The thrill of not knowing what might happen or who we might meet can create a sense of anticipation and excitement.