I'm a tap water drinker myself, but only after moving away from a city where water from other areas had to be imported to reach safe levels (according to EU regulations) because several garbage deposits of thousands of tons leaked for decades unhindered:

Almost 2 million tons of garbage, among that 40k tons of toxic waste: https://de.wikipedia.org/wiki/Fischer-Deponie

1 million tons aluminum & other stuffs: https://www.fcp.at/de/projekte/details/sanierung-altlast-n6

One might imagine that diluting such water to reach "safe" levels is not as healthy as water that never saw a toxic waste dump.

It's also not the case that tap water is always safe, even if it's declared to be. During hot summers, there's very often bacterial contamination, requiring addition of chlorine or other antiseptics. But until that is caught, some days might go by.