Monsieur Dior says -
For years pleats have been, and will continue to be, a high point of fashion. I love them because they are feminine, energetic and moving. They always give a look of simplicity that I like very much. They are very young.With pleats you may put the greatest fullness in a dress without making it look bunchy. They are very slimming and becoming to almost every woman.They are very versatile, too - you can have box, accordion, unpressed, inverted, and sun-ray pleats - and they all have their uses.
Photo: Vogue, March 1, 1955.
Source: The Little Dictionary Of Fashion by Christian Dior