In many cases it is symmetry, like in facial features, the most beautiful tend to have very symmetrical features.
And health, like clear skin, beautiful skin even as a teenager, good signs of health, beauty. 
Okay now, tcm, can I help it I inherited that?
"If it is once again one against forty-eight, then I am very sorry for the forty-eight." ~ Margaret Thatcher
“I predict future happiness for Americans, if they can prevent the government from wasting the labors of the people under the pretense of taking care of them.” ― Thomas Jefferson
