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?
I have an umbrella with a Bluetooth speaker. It even allows phone calls while using it. No idea why it’s a thing, but I found it could be fun to use as a rave-toy thing. Just gotta add some LED lights and choreography!