Why are females self conscious about breast size?

Since early ages: From the time kleenex got stuffed into trainng bras in adolescence to the age of media breast sexualization for adult women undergoing breast "revisions" women are very rarely happy about their breast shape, or size in much the same way many men have "penis envy". The breast is the most visible symbol of "femininity" for most women and a major psychological component of their "well being".