I once made a thread in regards to accepting compliments and possible issue surrounding it: http://personalitycafe.com/sex-relationships/472682-agreeing-compliments.html
The point was there can be an issue with acknowledging that one is beautiful or too strongly identify with such a sentiment without it having negative connotations in our culture. So it could be that whilst they acknowledge some standard of physical attractiveness, it's not socially acceptable to acknowledge.
There is also the issue that you don't really see yourself and thus your sense of self relies on external things, you construct a self image.
Žižek, Slavoj | Internet Encyclopedia of Philosophy
So we construct a sense of self, an illusory but necessary mask that you can't tear away.
Subject, Ego, Person | Philosophical Explorations
And so with this in mind, one can consider the transitory nature of a person's self concept.
People on here have shared how their sense of self took time to adjust to different feedback as their appearance or social context changed. Someone who has endured years of being told their ugly may maintain such an identity irrespective of others opinions or changes in their appearance. Similarly, someone may have a sense of being stunningly beautiful regardless of other's opinions.
So some people who look stunning now, may have gone through high school not feeling as such, so even if they appear stunning to everyone now, it doesn't just automatically shift to i'm the hottest. If anything, it can be jarring to a person's identity, in that they begin to question the feedback and what it conveys. Some become quite suspicious of people's emphasis and compliment on their looks considering that the supposed positive feedback they're getting now wasn't there previously.
This can be especially pronounced in the experience of those who change weights quite often and experience the differential treatment of being perceived as 'fat' in a cultural sense with its associations and 'skinny' with its cultural associations.
In this, one might end up feeling like the game of beauty is not fulfilling. To identify to strongly with the opinion of others gives them the power to take it away, making a precarious sense of self. If one feels too dependent on other's affirming that they're beautiful, then its of course a precarious sense of beauty in that it constantly must be proved.
To which many people might seek to emphasize other parts of their identity instead, to allow a more stable sense of self that doesn't jerk their emotions and make them question themselves too much.