People wear glasses because without them, they won’t be able to see the world around them clearly. This is because the shapes of eyeballs in some people are different. Hence, light which enters the eye is not focussed at a single point, resulting in blurred images. Glasses work because the lenses change the diffraction paths of light so that the light rays hit the back of the eyeball (retina) at a single point to create a sharp image.
I wear glasses because I am short-sighted. Without my glasses, the world would be a blurry mess! And I wouldn’t be able to do my experiments!
I’m short sighted too and walk into anything below waist height when I don’t have my glasses on. Some people wear glasses because they like how they look with glasses – fashion accessory! Some people because they need to, either to see close things or distant things.