Nobody is 100% the same on both sides of their body. Many of us have marked differences between our left and right sides, hence the celebrity requests to be shot on “their good side” and making sure that stars are filmed from certain angles. Beauty is measured in millimeters, and the slightest differences add up.
The more pronounced the differential, usually the more unhappy the person is with their feature in question. For women, it really hits home when breasts are noticeably different in size, something that can be camouflaged in clothing but when the clothes come off, what then?