3 mysterious sea shells... you think 3 dry sea shells (which most people understand logistically would be impossible to clean yourself properly with) was a stand in for bidets?

I was also around when the movie came out and not a single human i interacted with imagined they were a bidet. In fact bidets were so uncommon in the US at the time that most Americans experience with them was from the movie Crocodile Dundee.

Everyone's problem with the sea shells was that you wouldn't be able to clean yourself properly when you imagine physically using them. But people in the future they imagined have extremely small and limited diets, they probably don't produce an huge amount of waste. There's only 1 fat guy in the whole movie, and you wonder how Otho from Beetlejuice got that way on taco bell protein pellets.

IF they had introduced the concept of a bidet system, it would have immediately removed the mystery from the sea shells and made them far less intimidating.

The anxiety about bidets is leaving the bathroom with a wet spot on my ass.