It's clear that it's all because of Landau! He derived the formula for an ideal female figure:
L = (KMT) / ((N ^ 2) P),
Where K is bust girth, cm
P- weight, kg
Perfect result 4.5-6
Breasts are assessed differently in different cultures, for example in Ancient Greece, small breasts were considered especially beautiful. And the waist-to-hip ratio (WHR) is present in all paintings by artists of all time and ranges from 0.7 to 0.8. Researchers believe this is a measure of a woman's fertility. And some studies have found that it is more difficult for women with an OTB above 0.8 to get pregnant. More details about OTB can be found in the book "The Psychology of Beauty and Attractiveness" by Viren Suemi and Adrian Fernhem
Such standards came to us from the middle of the XX century. It is believed that the legendary Marilyn Monroe possessed just such parameters. True, she was short, so it's hard to call her thin. But over time, everyone forgot about growth, but the volumes stuck.
According to another version, these figures were chosen by fashion designers just for convenience, so that it would be easier to make patterns when sewing dresses.
Each time there were different standards of female beauty. For example, Rubensian ladies (XVII century) are women with a chest and hip girth of about 98 cm, a waist of about 72 cm.