One problem with relying on toothpaste, is that for many children, the parents are not good at parenting and don't provide tooth brushes/ toothpaste or enforce

One problem with relying on toothpaste, is that for many children, the parents are not good at parenting and don't provide tooth brushes/ toothpaste or enforce regular tooth brushing (and from experience, my teens/twenty somethings are somewhat hit and miss in this area as well since they moved out) Putting it in the water supply ensures most people will at least get some fluoride. One big problem not covered in the article, is this leads to fluorosis - my eldest has permanently stained teeth due to me not making him spit out his tooth paste after brushing when he was a toddler combined with the fluoride he was getting from town supply water.