Steak and Cheese

Why do so many grill cooks put so much mayonnaise on steak and cheese subs? All that is really needed is a thin layer on each side of the sub roll. What are they trying to cover up? Is the lettuce bad, the tomatoes? I don’t know, but I do get tired of having to be specific with the amount of mayonnaise that I would like on my steak and cheese or Philadelphia style chicken steak and cheese. For my taste, a little mayo goes a long way.