Lisa... hate to say it.. but it's NOT just Carnival. Most of the major cruise lines take the same position.
They write it down, but don't want to take the chance offending a passenger, so don't follow through.
On our Diamond Princess cruise in Aug. we did see people in shorts in the dining room at dinner.
On RCI we've seen coveralls worn on formal nights... but they did wear a hanky hanging out of the chest pocket <G>