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?
Just used one today to finish listening to a YouTube video while I was in the shower. It’s not a “bathroom” speaker per se, just a pretty nice Bluetooth one, Anker Soundcore Boost, with enough volume to rise above the white noise of the shower and ventilation fan.