Perhaps you were in the wrong bathroom. My sources tell me that the recorded flush sound has been a common feature of high-end ladies loos for many years.

It's not "useless" - it's actually saving the environment. How? It seems that some women use the sound of a flushing toilet to cover up the noises that accompany some bodily functions.

Replacing the flush sound recording with a sound clip from "When Harry Met Sally", could make for an entertaining Japanese TV show...