"The no-bra movement" of the 1970s was an eye opener 👀
source: pinterest
In the 1970s clothes were changing, sweaters were getting tight, and bras were burning. Even gals who weren't taking part in the women's lib movement got in on the action and gave themselves a break in the undergarment arena.
Since the advent of the bra, women have had to fit themselves into an uncomfortable garment that's been everything from pointy to pushy to padded so it makes sense that they just wanted to take a break from these strappy cells for a decade or so.
It helps that the fashion of the 1970s was geared towards a more relaxed, organic style. That kind of thing goes hand in hand with the abesnce of a bra which has to be more than kismet.