There's tap water, and then there's tap water. In my home town, the tap water started furring up the kettle from the first boil. You had to use twice as much soap as elsewhere.
Where I live now, tap water will kill tropical fish if you put them in before the chlorine gas has seeped out of it, and even goldfish aren't happy. You run the bath, and the smell catches your throat.
After a couple of hours standing, it is pure enough to put in a car battery.

We use a water filter with an activated charcoal element in it, just to be a little safer. And because I'm not waiting a couple of hours for a drink.