"Well, let's just hope he eats a bit neater than Ron or we'll be doing laundry all of the time." Harry had learned to eat neatly because of Aunt Petunia. Getting spaghetti sauce on his own face would have been asking to be taunted and criticized by Uncle Vernon, but spilling even a crumb on Aunt Petunia's floor would have been treated like he had just massacred a basket of kittens. Harry knew it wasn't worth the fuss and so he was careful not to be careless with his food.