2) An artificial sound to overlay embarrassing
farting sounds: Without this feature, it was
common for Japanese women to constantly use
the flush in order to create a louder sound.
This was obviously a huge waste water.
Was this an issue because Japanese walls are thinner? Or homes smaller? Farting isn't considered particularly appetizing here either but I don't remember a single time this has been an issue (or ever hearing someone farting from outside the bathroom).
The flushing is designed to cover up 'all' sounds. There's a lot of weird fetishes and taboos and hangups people have out here, so I wouldn't read too deeply into it. Diet is probably not a factor.
A combination of a collectivist culture and crazy expensive real estate leads to more people living in smaller homes and in closer proximity to each others bowel movements.
The Japanese diet also probably plays a role......
