Your post makes no sense. Ugly-average-beautiful scales don't work with supermodels. They aren't supposed to be run-of-the-mill good lookers. They're supposed to be striking, unique, and almost mystical. Controversial is HIGHLY HIGHLY important in modelling. It's a massive selling point if a supermodel is controversial.
Here's the reason: the most controversial beauty incites the most powerful emotion. Unique beauty is far more valued in our minds than more common beauty. Supermodels just wouldn't survive in a world like fashion, where vanity is taken to extremes, and everything is over-the-top, if they were simply an every-day good looker. If you've ever seen a catwalk you know what I mean. To compliment those crazy, extreme styles of clothing, you need extreme physicality. Hence why you've got the likes of Kate Moss, with slightly ****ed up wide eyes, sharp jawlines etc, and Rosie Whiteley, with that crazy (and ****ing sexy) pout.
To call supermodels 'average' highlights the point. Personally I think a lot of those are utterly gorgeous, and others are hideous. They're almost charactures in beauty. Asking the general public if they think these people are 'average' will never work. They're in modelling, because they're on the extremes of beauty, so you'll get extreme answers. It also highlights the point that beauty is almost entirely subjective (+1 to those that are anti-glamour).