I guess this is what I don't understand. Whenever this comes up, people usually act as if bottled water is no different than what comes out of people's taps. As the conversation goes on, though, people start talking about the filtration systems they've bought, or about having the water tested.

If we all know that tap water in many cases isn't the equivalent of filtered water, or that tap water can vary from location to location, why do these conversation invariably always start by pretending that there's no difference between bottled water and water straight from someone's tap?