Reproduction is understood as the maintenance and continuation of existing social relations.

. In that application, it is used to explain the role of women in wider social and class structures, and their (often unrecognized) contribution to the capitalist economy via their (traditional) role within the household as both child-bearers and family caretakers, and by extension women's role as providers of free labor that is necessary to produce and maintain current and future workers.

Men wouldn't obsess over women's breasts if they weren't taught to by society, simple as. Plenty of cultures didn't have this phenomenon, and think that it is weird that people do that.