On Tap Water vs. Bottled Water

I have a simple question:

If tap water is better for you because it’s better regulated why is it that in various places across the country the tap water tastes like different kinds of crap, while a bottle of Dasani always tastes exactly the same?

I want to believe in tap water, but until you can explain why there is so much variation and so foul a taste in most tap water I must go with the option that tastes good consistently, i.e. bottled. ::