After the civil war, the super-rich wife ruled the upper class with an iron fist. However, as more and more people become millionaires, it is difficult to distinguish respectable old money families from vulgar new money families. In the1880s, in order to distinguish who can accept and who can't, women who have become "popular" think it is necessary to make dozens of fashion rules that everyone must abide by. In this case, if a woman shows up at the opera house, her skirt costs more than most Americans a year, but the sleeves don't fit, and other women will know not to give her time.
White is one of these stupid rules, except in summer. White is suitable for weddings and holiday costumes, not autumn dinners. Of course, it may be very hot in September, and wearing white may be the most meaningful, but if you want to dress appropriately, you don't do it. 1894 labor day became a federal holiday, and society finally regarded it as the natural end of summer fashion.
Not everyone abides by this rule. Even some celebrities continue to go against the trend. The most famous is coco chanel, who wears white all the year round. But even though this rule was initially applied to only a few hundred women, it has gradually penetrated into everyone else in the past few decades. In the 1950 s, women's magazines made it clear to the American middle class that white clothes were dug up on Memorial Day and put back in the warehouse after Labor Day.
Nowadays, the fashion world has relaxed a lot about what color to wear and when to wear it, but every year after Labor Day, you will still hear people say that white is unacceptable, thanks to some snobbish millionaires who think it is more fashionable than 100 years ago.