Caravaggio painted in a style called tenebrism — the figure emerging from blackness, light hitting only a face, a hand, the edge of a sleeve. The rest of the canvas isn’t sky or wall or room. It’s just dark. There’s no background, only absence.
The technique solves a problem. In a fully lit scene every relationship in the frame has to be resolved — the wall behind the figure, the floor under the table, the cloth on the shoulder, all in coherent light. Get one of them wrong and the picture feels off. In darkness most of the canvas is the same value. The composition narrows to the few lit points. Fewer decisions, fewer chances to be wrong.
It isn’t a shortcut. The lit areas have to do more work — they carry the entire picture. But there are fewer of them, so each one can be exact. Caravaggio’s hands and faces are exact because they have to be. Nothing else is.
The same asymmetry shows up in CSS animation. A dim glow against black is forgiving. The same glow against white shows every wobble in the math. Low contrast in a bright scene reads as muddy; low contrast in a dark scene reads as atmosphere.
Most of the picture can be the same dark and still be a picture. That isn’t true of light.