The Wall Street Journal reports on 'The Tricky Chemistry Of Attraction'.
Much of the attraction between the sexes is chemistry. New studies suggest that when women use hormonal contraceptives, such as birth-control pills, it disrupts some of these chemical signals, affecting their attractiveness to men and women's own preferences for romantic partners.
The type of man a woman is drawn to is known to change during her monthly cycle - when a woman is fertile, for instance, she might look for a man with more masculine features. Taking the pill or another type of hormonal contraceptive upends this natural dynamic, making less-masculine men seem more attractive, according to a small but growing body of evidence.
There's more at the link.
So that's why metrosexuals became popular! It's all the Pill's fault!