When I had a boat with a bath I would have showers when moored and a bath when I went to the water point.
I would fill up, move away from the water point, have a nice soak in the lashings of hot water heated by the engine, do my cleaning chores then go back and fill up again ready for the next two weeks.
Baths are also good if you do a lot of winter cruising as you can have a nice hot soak everyday if you want.
I also used to do a lot of hand washing of clothes in the bath but it takes its toll on your back. They also make a useful place to hang clothes over to dry.