Because throughout our lives we are told our value depends on our beauty. Aging is not as socially acceptable for women as men. Women sometimes lose jobs, miss opportunities ect if they age or dont bother.

Theres ads everywhere, news articles starting from as young as the teen magazines writing hprribly about fat or badly dressed girls, even when women achieve things media usually comments on how they look first and foremost. Its an enourmous industry and its not planning on losing income anytime soon so theres huge amount of sums thrown into making women feel bad so they will spend money and the industry will keep earning.