The motto of informality is: ‘Let’s do things the easiest, most convenient way and never mind how they seem, because nobody is paying attention, anyway.’
Formality says: ‘Yes, it does matter, and the surrender of individuality to high group standards is a trivial sacrifice to the overall beauty of the thing.’
Miss Manners, “Why Not Try a Formal Picnic for a Change?” (1986)
(thanks, Mark)