Do you think that someone sits down and makes a list of all items that need to be labeled as containing X, which is then updated each time a new food or recipe hits the store shelves?

Or is it more likely that regulators simply state that all foods for human consumption containing more than some percent by weight of X must be labeled as containing X?

If your goal is to ensure that consumers are alerted to certain ingredients for allergy or other purposes, you care very much about a product not getting labeled properly, and you don't really care if something obvious gets the label.

I'm not really sure why this is so hard to grasp...