yet something like fluorination effects 75% of the water supply and its only real benefit is fewer cavities

That was only a suspected causal relationship based on study of primitive people with good teeth and a corresponding high level of natural floridation in the local water. However, it's now suspected that that wasn't the cause. In fact, flouride is starting to be linked with some forms of mental illness

One reason we go to dentists that don't use flouride and drink bottled water and use non-flouride toothpaste