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’m using a JBL flip which I just leave outside the shower on a shelf. Waterproof enough that I can adjust the volume by just reaching past the curtain.