I agree, I do believe it is just what you are used to. I have never drank tap water, even as a child living in texas, my father paid to have filtered water delivered to our home. Now i do the same thing, except I go to a place and have my 5 gallon jugs refilled with filtered water. But i do buy distilled water from the store and drink as well.
I have tried numerous types of bottled waters, they all taste the same to me, sweet. But yes, I agree, it is what you are use to, and everything else will taste "different"