Another side effect was that you always knew when the bathroom was in use (aside from someone forgetting to turn the light off, which you now had radio playing to remind you off).
But why and how did we become bothered by the _sounds_ of it? Are you bothered by the coo-coos of birds, or morning rooster calls. Cats purring, screeching cat calls or dogs barking? All of these can be similarly annoying, but we are not "solving" them.
It's weird how our association of sounds with smells and dirtiness of taking a dump has made sounds which are rarely that bad in objective sense (loudness, pitch...) so unpleasant.
It's also how it's considered impolite to slurp a soup, and some people are outright disgusted by hearing it being done.