Why are beautiful people criticised for their looks more than others?

I've noticed, that the people most criticised for their looks by other people are physically attractive. For instance, if a hot celebrity like Beyonce gains weight or makes some other appearance change, people will be overly critical and pick out their flaws. Moreso than if it were a less-attractive person- most people wouldn't even notice. Do you think this is true, and why does this happen?
Why are beautiful people criticised for their looks more than others?
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