I don't know that contaminated water happens very often, but many people are partial to the taste of their own water. If you get water that doesn't taste like what you are used to, while it is not contaminated, it tastes bad.
I grew up on well water, and also Cleveland, OH water. After well water, the water in Cleveland always tasted bad to me. That was the worst water I have ever had, that I can recall. I will drink any water, but enjoy my Denver water or well water, the most.
I travel with full tank and water heater. We boondock most of the time, and I don't want to mess with finding, then filling, on the road.