

Because it’s easy. We enrich lots of stuff for public health. Breakfast cereals have tons of extra nutrients, vitamin d is put in milk, white rice and flour are supplemented to offset the loss compared to whole-grain. It’s mostly done in response to lots of children in poverty getting sick.
But there’s no reason to avoid them. Flouride in water is safe at the regulated levels and has a measurable impact on dental health, just like enriched milk safely reduced the incidence of rickets in children. If you need pure water you can buy distilled gallons but clean, healthful tap water is a modern marvel.