Think about this, though. Would the same group of characters appear more legitimate or interesting if they were ugly? If people are attracted to and obsess about beauty in real life, why wouldn't they in a fantasy? And the people behind the computer screes, who play these characters, are they not teenagers or young themselves? How much depth should you be able to expect from them? I'm not trying to be snarky here, genuinely interested in these questions.
You didn't ask me, but I feel inclined to respond.
I think that attractive characters aren't a problem in themselves, but can be a symptom of another problem. If a character is really super totally hot, but their attractiveness doesn't have any interesting implications on their personality, it
could be an indication that someone is playing for wish-fulfilment more so than to create a good story. Chances are, they're just playing an idealised version of themselves, whether they realise it or not. And that's usually detrimental to good story-telling.
For the second point, there's a notable difference between someone playing a character who is snarky teenager, and an actual snarky teenager playing themselves. The former person knows he's playing an annoying character, assumably with the intention of making them less annoying through character development. The latter person probably thinks the way they're acting is actually cool. Their perspective is limited due to their inexperience, and if they don't see the flaws in their own character, they're unlikely to create any interesting development.
These are generalisations, of course. Point is, the problem isn't about snarky teenage supermodels specifically, but about the fact that they are statistically likely to overlap with a miasma of bad roleplaying practices.
