Lingerie is sexy. Sex sells. It's therefore intuitively obvious to the most casual observer that money may be made from selling sexy underwear. For example, Lady Duff-Gordon, a survivor or the sinking of the Titanic, made money from selling bedroom wear to rich women early in the twentieth century. Victoria's Secret is making money doing basically the same thing for today's women.
While little black dresses and lingerie are each sexy by themselves, panty/bra lines in combination with little black dresses are not.
Thongs are a groundbreaking invention in lingerie technology.