But is a perceptual colorspace "natural"? A physics-based vectorspace is the most natural thing. Adding vectors in a perception based vectorspace seems unnatural to me.
Our human colour perception is very much not based on the physics or mathematics of light [1] [2]. It evolved to keep us alive and breeding, not to be accurate or precise about what light and colour actually are, so what is "natural" really means how we in particular see. For anything intended to be viewed by people, perception is all that matters.
Our computers, phones, TVs, etc. are designed specifically for human eyes, and other animals looking at them won't necessarily see the things portrayed with the same colours they see in reality.
Lab is not energy linear, and if you're doing rendering/illumination, you won't want to use Lab (unless you're deliberately trying to stylize). It is designed to be a good model of human color perception, not the physics of light.
Lab color space is good for mixing colors in a way that behaves intuitively. E.g. "what color is 'halfway between' these two other colors?", mixing "paint" digitally, producing pleasing gradients, picking colors or creating palettes.
