When Givenchy dressed Audrey Hepburn for her role in Blake Edwards’ 1961 film, Breakfast at Tiffany’s, luxury was still exclusive, the particular provenance of the refined social elite. Wearing couture specially tailored to her slim and graceful frame, Hepburn exemplified the allure of luxury even as she played a character who could only dream about it: In a classic Hollywood paradox, the world Holly Golightly glimpses through Tiffany’s window is the one Hepburn is wearing.

By 1980, all that was changing. When Brooke Shields announced that nothing came between her and her Calvins, the message was not that Calvin Klein jeans were for her alone — it was that they were for everyone.…