Tyler Cowen rhetorically asks whether anyone would buy fluoridated water:

But hey, when you buy bottled water isn’t fluoride what you’re trying to avoid?

It may not make sense in urban areas, but if you get water from a well (or even from some rural water utilities), the water isn’t going to be fluoridated. Presumably, this product is aimed at parents in rural areas (or who live in areas with bad drinking water supplies, like Washington, D.C.) who want their kids to have more cavity-resistant teeth. So it makes sense to me, at least, especially when you consider the alternative is trying to make your kids take fluoride tablets every day (something I had to do while growing up).