Seems pointless and inconvenient for me as they usually seem to be poor quality, and can you really listen to music in the shower, and are you showering long enough to benefit from it?
Or do you own one and use for a different purpose, like swimming or Kayaking?
Or camping, OMG. The people who set up at a national forest and start blaring shitty music.
Unfortunately lots of people lack self awareness. I do honestly try my best to not be one of those people.