My messy birds get hanging or mounted waterers. My others I dump daily if there is poop or lots of dirt in there. If it's mostly clean (a feather or two and a few grains of dirt count as clean to me), I just fill it back to the top. Some birds are just godawful about making messes, others are so clean it's amazing.
As for it not being how they would drink naturally, true, but I can almost guarantee that the climate, their feed and their housing is not what they would do naturally in the wild as well, so....
As for it not being how they would drink naturally, true, but I can almost guarantee that the climate, their feed and their housing is not what they would do naturally in the wild as well, so....