Incidentally, the strange thing is that there is no way they can guarantee an allergen-free environment. People are bound to make mistakes. I wonder if it is more about liability than anything else?
I think this is part of it, we probably all know adults who have severe anaphalytic reactions to nuts (I do, and also to seafood) but there were never any food bans when they were children, the main difference is that attitudes towards liability are very different now.