I agree with you. But what if you want to drink pure/purified water? You can do for little to no cost in certain conditions, but for city people there are either bottled water or some purifying systems that can be costly and of various levels of efficiency. Then, how much water does one liter of water costs?

But then you could argue that people don't need to drink purified water, tap water is good enough, lead levels, chlorine levels (etc) are low enough. But this is another question from the previous one, that should also be discussed taking the whole picture into account.