Ketchup on a hot dog is far worse. I have tried some kinds of mustard on steak, and really if it's mediocre steak, it's about the same as Heinz 57 in concept.
I grill those Eckrich pork sausages on occasion and she brings out the mustard arsenal. She likes them, of course they are fatty as H.
She doesn't like the onions I cook with them though, she wants onions cooked to smithereens, and steak blu rare, which is super rare. I'll do one of those strips tonight and cut her a piece first and barely cook it. I still marvel how hot that electric grill gets, but I guess it's akin to the broiler in the oven.