A couple of years ago Disney changed all the kids menus. All grilled meats, raw vegetables, chicken pita pizza (there was a lot of discussion about how kids won't eat chicken on pizza and didn't understand why their crust was different), desserts were either apples, yogurt or sugar free jello. Those menus got changed back to macaroni and cheese and chicken nuggets with cookies, ice cream and pudding added for desserts pretty quickly.
I suppose guests are swallowing the buns more readily than they swallowed that.