Ask and Guess
Does the Euphemism Treadmill fit your idea of etiquette creep? It refers to the process of euphemisms gradually coming to be perceived as no less rude than the expressions they originally replaced, leading to the adoption of shiny new euphemisms to replace them.
It's plausible that etiquette creep is the mechanism by which such cultures became Guess cultures in the first place. The other mechanism I can think of is etiquette arms race: basically, mastery of etiquette is how you signal your social acuity, and if it comes to pass that everyone in your culture knows the rules it becomes neccesary to make them even more complicated so that the signal doesn't lose it's value.