The main advantage of RV wet baths is saving space. Since the shower does not take up additional room, it is possible to put a wet bath into a small RV.
They other benefit of RV wet baths is that they are super easy to clean. Since everything gets wet when you shower, there will never be any dust build-up.
While they have many downsides, an RV wet bath is better than no bathroom at all. If a wet bath is the only option for your desired RV size, then it is a great option.