I still don't understand why these can be sold in American pharmacies.
Because every bottle is clearly labeled “The FDA has not evaluated this for treating any condition”. There are a great many products that the FDA hasn’t evaluated that are still sold, why should these be any different?
They need to avoid making claims that they can treat or diagnose some condition. They do their best to hint at it without crossing the line, and frequently blatantly do cross it. The FDA does not have anywhere near the manpower to enforce it. And when they do finally get around to it, the brand vanishes, and a new one appears with exactly the same product lineup.
The sector has long lost any entitlement to benefit of the doubt. They are knowingly making illegal claims and using a disclaimer as a fig leaf even though everything else on the package contradicts it.