Almost every fairytale worth its name has a ball, not just a party. There is just something about the idea of a ball, from the gowns to the music, that has an air of style and elegance that is missing in a party. A ball gown sounds much more beautiful than a party frock.
It is all about perception, connotation and implication or the emotional weight of the words. Attend a ball and live the fairytale.