I once looked carefully in the mirror to try and see what was causing the dark circles under my eyes -- were they discolored skin perhaps due to veins near the surface? When I shined a light on them from beneath, the dark circles disappeared.
Apparently, the dark circles are shadows. They increase with age as baby-fat (and later, muscles) around the eyes shrink. I suppose sadness or fatigue makes them worse due to decreased facial muscle-tone. Inheritance is also a factor, as this determines the shape and contour of one's face.
To hide the shadow, women increase the reflectivity of the skin under the eyes by applying light-colored make-up. This makes them better resemble very young women, though it might look weird in a room where all the illumination came from the floor level.
Filmmakers make actors look younger through a combination of make-up and set-lighting. (You are not going to notice wrinkles if light from a variety of angles ensures that the shadows are all filled in.)