Is it not the same for paying for food, as well? I generally agree, but water seems an arbitrary line to draw when we still have shelter and food to consider.
Before humans decided to pollute a lot of the fresh water on earth or appropriate it for themselves, humans could just go to the nearest stream and get water. In that sense, it feels right that it should be easily accessible at no cost. Meanwhile, humans have usually had to expand considerable effort to build a shelter and gather or grow food. So i don’t see the line as being arbitrary.