Oh and if somebody asks about "but what about chlorinated tap water" - that is less common in Germany. I cannot detect anything but "water" in the places I visit in various German states. Anyone concerned about such things can get a water filter, they are plentiful in supermarkets, mostly these types: https://i.pinimg.com/736x/31/ed/ff/31edff1af777601ac16d33292...
The website of my own municipal water company (of a large Bavarian city) says water is chlorinated only when it is absolutely necessary, and that if they do it they will also stop as soon as possible. So that is a temporary measure when something happened but not usually done.
We (in Germany) do have a nitrate problem in a lot of places. We even got reprimanded by the EU about that only recently. The reason is agriculture, of course. (https://www.euractiv.com/section/agriculture-food/news/eu-cl...)
When I was a kid, my parents would only buy carbonated water. Still water was available from the tap. Today, I stopped buying even that, I can carbonate my water myself.
As to why we buy so much bottled water: Marketing. Some waters have a distinct taste, but at least for me, it’s just a matter of getting used to a different tap water taste when moving.
https://www.amazon.com/SodaStream-Sparkling-Water-Starter-Si...
[1] https://www.spiegel.de/wirtschaft/unternehmen/mineralwasser-...