The laziest answer is just "pop culture phase". Remember when people wouldn't shut up about metrosixuals? Remember the 70's? Maybe not, but you've probably seen many things making fun of the era and its big hair and big pants and whatnot. Or perhaps those stereotypical depictions of the 50's, where men all had square heads and smoked a pipe and were incapable of saying anything that wasn't either fatherly advice or dismissive patronizing of women. Or for a more modern example, look at Justin Bieber. He's one in a long line of manufactured pop stars, specifically designed to target the desires and wallets of a specific demographic. Much as some people act like ridiculous drama queens hating him and his supposed lack of manliness, it doesn't change his popularity, or the waves of functionally identical singers that came before, and will likely follow.
Things are similar in Japan. Corporations churn out glam boy-bands in a simultaneous effort to both cash in on, and sustain, that current fad. I see a lot of westerners decry this look, because they are apparently absolutely certain that what a man trying to look attractive should look like has nothing to do with what women find attractive, and the legions of female fans are just a coincidence. A lot of what people "should" look like is just passing fashion, and that's the fashion; what appeals to women, and what's a goal for men, until fashion dictates something new.
Also worth noting is the all-male nature of Kabuki theater, in which women were banned from performing. In order to put on shows that had female characters, the more feminine-looking actors simply dressed as women. This was done for hundreds of years, and the role of the androgynous male became its own separate, distinguished part, one with its own fans and which people expected to see. I would assume it's a normal part of their culture to expect a few characters who fill that role, and as was mentioned above, to expect protagonists in that role because fashion has made it popular for the moment.