Because not everyone is like you. Not everyone has the eeucation you do. Not everyone has the same means to buy beneficial stuff. Not everyone takes the kind of care they should of their children.
Flouridated water, by most accounts, has had a really positivie impact on public health.
We should do our best to make sure our water supply is well funded and monitored. Unfortunately, more and more water systems are privatized and clean drinking water and corporate profits don't seem compatible to me.
But we should be pragmatic and clear eyed. I worry to see phrases like "I don't care what anyone says" in a scientific context.