Allergen labelling is a huge blessing to anyone with serious allergies. Yes, labeling A Package of Allergens with 'Contains Allergen' might feel weird, but it's critical for non-obvious ingredients and contaminants.
So for consistency's sake it's better to just always list allergens, rather than have the regulations say "except when it's bizarre and nonsensical." Otherwise, someone has to decide where that boundary is.
I don’t think it’s really that hard to draw the line. You can still err heavily on the side of safety while not requiring a bag of nuts to warn about the nuts it contains. But our legal system doesn’t go for that sort of nuance.
