Comment by Cthulhu_
Fluoride treatments at the dentist and fluoridated tooth paste are a big factor in my area. A commenter also mentioned fluoridated water, which had the same objective, but it causes demineralization of teeth (fluorosis) and possibly behavioural / hormonal changes (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520156/, https://www.sciencedirect.com/science/article/pii/S001393512..., https://ec.europa.eu/health/scientific_committees/opinions_l... ). I'm glad fluoridization of water isn't a thing where I live.
First, fluorosis isn't demineralization of teeth, it's hypermineralization, way on the other side of the spectrum.
Second, you'll get water poisoning before you'd get fluorosis from tap water. I challenge you to find anyone who has gotten fluorosis from tap water alone