Are younger minor siblings in the household at play here? If yes, I get the separate sleeping arrangements in this situation, setting an example, certain family beliefs, etc. Honestly though if you're an adult, you should just hotel it if it's going to be an issue for the parents. You basically know whether it's a good idea or not. Otherwise, it's hosts house, hosts rules, and suck it up buttercup.

A minor inconvenience for a basically free stay. Could care less if our adult kids sleep with their SO, married or not under our roof. For us, sex isn't taboo.