Age Range in Male and Female Couples

There have always been cases of relationships between men and women where the age differed greatly. In society it seems like no one flinches an eye when an older man is with a women of a considerably younger age, but when the woman is older and the man is a lot younger heads seem to turn. Take regular old college students for instance. If a male college freshman is dating a girl younger than him that is still a senior in high school it doesn't seem like such a big deal, but if a girl in college is dating a guy still in high school questions arouse. Even on a bigger spectrum of life the same responses are received. Like in celebrity couples such as Demi Moore and Ashton Kutcher or Cameron Diaz and Justin Timberlake which in both cases the women were much older. Those couples seemed to get way more publicity than ones with way older men. Celebrity couples with men much older don't even come to mind. Except for Hugh Hefner and his tons of playboy girlfriends. People only seem to register him because playboy is so popular as well as the television show they now have on E!. Why is this? Why is age such a big deal?