Ohhh I so did!!!!

"It is useful for something (given that salt added to processed foods is iodized)"

Seweed is the best source of iodine I know of, it is also in some saltwater fish, milk and yogurt (because iodine is added to the cattle feed I believe) and by the same token, some meat if it grazes by the sea (where it is present in the soil and the animals ingest it), same for veg grown in iodine rich soil (although iodine levels in US soil are far lower than they used to be). As most people don't eat seaweed on a regular basis, have no real way of knowing what the iodine levels are in our veg and meat, especially inland, and many people don't eat saltwater fish that often (especially given mercury scares), iodized salt was seen as a huge advancement to preventing iodine deficiency, and the symptons and diseases it causes.