Why are breasts private parts?

There are a few cultural and social reasons why breasts have come to be considered private parts.

For instance, many historical, artistic, and social traditions depicted breasts as erotic objects. This sexualised perspective led to cultural norms, rules, and laws regulating public displays of breasts.

Also, some societies associated femininity and sexual maturity with women’s chests. Covering it could mean protecting women from scrutiny when entering spaces dominated by men.