I know of a couple of areas don't have very good tasting well water(sulfur), and one that has downright dangerous water(natural occurring benzene) .  Bottled water is at least tested. 

.In Africa we only drank bottled water due to lack of adequate sanitation of public drinking water. 

I have had visitors from third world countries that looked at me like I was crazy going to the sink and getting a drink!  I had to explain to them that in the US most water is perfectly safe.