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?
Eh, pointless is kind of a matter of preference. It’s something you either want, or you don’t. There’s no point beyond that.
The inconvenience is no greater than it used to be for other types of portable music sources. Folks have been using radios and “boom boxes” in the bathroom for longer than I’ve been alive. My mom had a small radio she was allowed to use in the bathroom when she was a kid in the 50s.
It’s also more convenient than playing the music extra loud from another room.
But, yeah, if you’re just hopping in and doing the bare minimum as fast as possible, it would be an increase in effort beyond the reward of music for most people. You’d have to be the sort that just always has music playing for it to be “worth it” to switch to a dedicated shower speaker.
Mine is a fairly general purpose unit that is shower proof. I bought it specifically for use in the shower (though it’s rarely in the shower, I prefer to place it elsewhere most of the time), but it isn’t advertised as a shower speaker. Most of those that are tend to be kinda meh sound wise, and/or lack any bass at all. I also use it in the kitchen while cooking, unless I’m the only one home and can really crank my main system up.
But, yeah, lots of people have dedicated units of some kind.