The science behind study of what is beautiful often looks at the Golden Ratio. This is based on Fibonacci Numbers, where every number in the sequence (after the second) is the sum of the previous 2 numbers: 1, 1, 2, 3, 5, 8, 13, 21, ...
People’s faces have been mapped and those that more people agree are beautiful are regular and symetrical and have proportions that follow the Golden Ratio. So for example their two front teeth are double the size of the two teeth on either side of them and all sorts of other ratios between the different elements of their face. The more someone conforms to this, the more beautiful we find them.
I think that make up will emphasize features, making them appear to fit better into the Golden Ratio. And obviously photoshop will too…