Why are ancient Korean costumes so open?

At the beginning of the last century, American missionaries used the most advanced photo bleaching technology at the time to take photos of North Korean civilian life. At that time, there was a kind of women's short coat worn in summer that exposed breasts. Beauty is about exposing your breasts and exposing your breasts. It was banned during the Japanese occupation.

Possible reasons:

(1) Traditional customs and habits. It can be seen from the painting that this kind of clothing has existed since ancient times.

(2) Convenient for breastfeeding. It can be seen from the photos that unmarried women do not wear them, but married women do.