Why aren't restaurant staffs taught about food allergies? Because it seems like many of them think that "allergic to X" means "allergic to X cooked into the food," not "also allergic to X used as a garnish, rubbed onto the serving dishes, trace remains on the chopping knife, brushed off when the diner complains..."
Yes, I know that people use "I'm allergic to X" when what they mean is "I don't like X" because allergies are seen as more acceptable than food dislikes. But dear gods and little fishes, if a person truly DOES have a full-blown epi-pen-at-the-ready allergy to X, then even trace amounts can KILL them!
One time I pulled into a fast food drivethrough, asked if the chicken sandwich had mustard, and was assured that it did not. Got down the road, bit into the sandwich -- honey mustard. I turned around, parked and went in, and the staff said "But it doesn't have mustard! It has honey-mustard!" I got the food comped and a replacement only when I pointed out that it was lucky for them that mustard only makes me barf, because if it had caused anaphylactic shock, they would now be paying for my ER visit and/or funeral.