Well, not exactly unique, since billions of people have them, but I know what you mean. My daughter has single eyelids, and everyone agrees she is beautiful. There are all sorts of people in the world, and there are beautiful and not-so-beautiful people with all sorts of variations of eye and nose shape, skin tone, hair color and texture -- and yes, body size and shape!
It makes the world a much more interesting place. How boring (not to mention confusing!) it would be if we were all the same!
Why is there this perception? Well, it is mostly the media. Movies and tv show promote only a very limited range of looks as attractive. So any child (especially girl) growing up bombared with these images, starts to think of herself as less if she doesn't match them. So there are 10 year old girls and even younger that are dieting, and wanting breast implants and plastic surgery -- craziness! And really sad also.