I agree with "because it can afford to be now," but in a different sense. It's fashionable to be fat when food is scarce, and thin when food is abundant. It's fashionable to be pale-skinned when the lower-class works outdoors, and tanned when they work in offices. And it's fashionable to be shiny and realistic when it's a hard effect to implement, and flat when shiny realism is one library-call away.