In some genres/media of RP it's kind of necessary, too, I'll add.

If you play females in anime/manga-tagged games then I [i]defy[/i] you to find an ugly one, or even a plain one. Unless you're playing a cartoonishly gross character like [url=http://images4.fanpop.com/image/answers/999000/999979_1286189058011.66res_500_281.jpg]the Witch of the Wastes[/url], you basically can't. There [i]is[/i] a middle-ground between "drop-dead gorgeous" and "a hopelessly hideous hag," but it's slim as fuck, and even then, in all of these cases their ugliness is a defining aspect of their characters, so it's not like they're ever ugly incidentally.