Since ancient times, models are basically thin. In the 1980s, internationally recognized good models were tall and thin. In 1990s, the trend of "morbid beauty" pushed "thinness is beauty" to the peak of fashion. At that time, the models were basically skinny, but with the development of the times, the requirements were not so morbid. However, thin models are still popular in the modeling circle, and most people think it is a symbol of fashion. So the supermodels we see now are basically thin, which also leads to their relatively flat breasts.
Then the model's job is to show clothes, and the "flat figure" model has an advantage in this respect. A plump model will destroy the original shape of the clothes and even wrinkle them. This is what designers and audiences don't want to see. In addition, if the model is too sexy and charming, the audience's attention may be drawn away. The audience's attention is focused on the model, while ignoring the clothes displayed, which the designer doesn't want to see.
In Europe and America, the handsome and cool "neutral wind" has always been favored by girls. For example, whether it is sexy and beautiful keira knightley, fashionable and bold ladygagaga, or popular mildew, they are all flat bodies. Therefore, influenced by international fashion, flat chest has become a symbol of fashion. As a supermodel at the top of the trend, you must keep up with the fashion trend.