Fluoride attracts calcium which is why it's good for your teeth. But it shouldn't enter your blood stream. It leads to calcium deposits on the pineal gland in the center of your brain.

With fluoride toothpaste easily obtainable there's no reason to drink fluoride. 

Also there's no medical or scientific basis for medicating a public water supply. For one thing, you can't control the dose. One person drinks ten glasses of water a day and another person drinks one or none. You're giving the same concentration to a 2 year old, a 30 year old, or an 80 year old. 

Also the fluoride in the water is not the same as the fluoride in your toothpaste. Fluorosilicic acid is a toxic byproduct of aluminum manufacturing.