If the earth is round, and the surface of a table is not, than gravity would have a great er effect at the point closest to the earth. This would then mean that the center of the table is under a stronger pull, and objects, particularly round ones would have a tendency to move to this point. In order for gravity to operate equally on all points of a table, or any other flat surface, it must be rounded to the same degree of the surface of the earth on which it is placed.