I don't remember the source, but I recall reading that, paradoxically, tap water in cities is much better quality than bottled water, due to stricter controls. Probably doesn't taste as good, but you can be quite sure it won't harm you.
The tap water from the small village in the Italian country I was born in is the best I've ever had, but I drink straight from the tap in London without any issues, except when I need to satisfy my craving for sparkling water.
You are referencing water standards in the USA. Each water type fell under the authority of a different Federal agency. EPA for tap, FDA for bottled, I believe. The FDA has lesser standards. My thoughts are because, at the time, only suckers would pay money for something that was practically free.
In any case, the standards have now been made the same.
The tap water from the small village in the Italian country I was born in is the best I've ever had, but I drink straight from the tap in London without any issues, except when I need to satisfy my craving for sparkling water.