Why "Drop-Dead Gorgeous"?

My previous post, a CFBA review of Ariel Allison's eye of the god, brought a pet peeve of mine to the forefront of my limited attention span. That being: Why does genre fiction invariably ... as in, most always ... portray the protagonists as drop-dead gorgeous. Take eye of the god, for instance: Dr. Abigail Mitchell is so striking that reluctant jewel thief Alex Weld can't help falling in love with her. And Alex's athletic physique and rakish grin make him irresistible as well.         Of course, the story wouldn't have worked if Alex had sported a beer-guzzler's gut and thinning hair, balanced out by a five-day, grayish shadow on his triple chins. But what if Dr. Mitchell had been too tall--even in sensible shoes--too thin, and constantly battling psoriasis and unruly, ratty-brown hair. What if her years of scholarly pursuit in dimly lit library aisles had forced her to wear Coke-bottle-bottom glasses. And what if she was painfully shy because she was always the smartest person in the room?         What if Dr. Abby Mitchell, despite her obvious appearance shortfalls, possessed a quirky sense of humor, a disarming smile, and without the glasses, eyes in which a guy could get lost. What if her apparent vulnerability had shaken hard-as-nails jewel thief Alex Weld's resolve? And what if his worming himself into her life--and her bed--had revealed a carefully hidden personality and caused her belated blooming into a beautiful "swan." Without changing the story's plot, that would have transformed a pretty good story into a truly memorable one.