“swimmer” bluetooth speaker in particular can be quite useful in all kinds of places. You can use a waterproof Bluetooth speaker to listen to music by the pool, or to take calls on speakerphone. You can take these waterproof Bluetooth speakers in the shower, use them by the beach while working out.
Some people even bring them camping. Even if you don’t plan to take them anywhere wet, a Bluetooth speaker with waterproofing is more likely to survive accidentally splashes of water than a regular Bluetooth speaker. If you’re buying a Bluetooth speaker, it just makes sense to buy one that’s made to be water-tight.