Some Anglosphere countries (USA, Canada, Ireland, Australia) love to add fluoride in water. They say it’s good for people’s dental health.
Europeans (Germany, Finland, Italy, France, Netherlands, Switzeland) think it’s wrong/unethical.
There is actually regular controversy around this
https://hsph.harvard.edu/news/fluoridated-drinking-water/
Do they put fluoride in your drinking water ? Are you happy with that?
Untreated tap water? It’s a new infrastructure I guess because I don’t think you can do this an older one
You can, provided it’s a good source