Answer: Lots of things! I made a list.
1. They reinforce the artificial gender binary.*
The vast majority of bodily modifications demanded of women by our beauty standards – for instance, plucked eyebrows, painted lips, shaved legs, and exaggerated eyelashes – exist to accentuate the differences between men and women. Fashionable clothes for men and women are vastly different, with most women’s fashions being tailored to highlight and emphasize “feminine” shapes.
Not only is this dichotomy unfair (the burden of highlighting gender differences, in time and resources, falls disproportionately on women), it’s outright harmful to trans* and intersex people. When our beauty standard pushes people to the outside edges of the gender spectrum, it renders those who live in the middle invisible and tells anyone who doesn’t comply with rigid gender roles that they are “ugly.” That’s a major problem.