It turns out they just don't really drink water. It's always something in a can - flavored seltzers or soft drinks.
It kinda blew my mind that there are people out there who don't drink water. It feels as natural as breathing to me.
It is still the main beverage we drink, and there are still those who never drink it. Incredible.
On the other hand, NYC and SF both have excellent tap water. And other cities are somewhere in between, or at the extreme end can even be dangerous (Flint MI).
The same is true of well water. Some of the best-tasting and perfectly safe water I've ever had has been well water. And as you mention, it can also come in all sorts of off-putting flavors. And it can be contaminated and dangerous (biologically or chemically).
People talk a lot about the variations of coffee or wine or beer, but I think the variations in water are even more interesting (and sometimes contributive to the others).