But tap water is simply not good enough for some.
This is the reason Perrier and Evian bottled water gained traction in the 80's with yuppies IIRC. Nowadays having established the principle that refusing to drink tap water in favour of stuff in bottles shows one up as being a better and more discerning human being than those who can't tell the difference, Perrier and Evian have gifted us the idea that ANY water in bottles no matter how cheap and is somehow better than tap. So now we have people drinking bottled water but choosing it entirely on price, when the best quality water is piped straight into they house. A triumph of marketing over common sense.