Have you ever changed the order of two CSS rules and broken a component without changing the logic? .btn :hover { background : dodgerblue ; } .btn [ disabled ] { background : gray ; } Both selectors have specificity (0, 1, 1) . When a button is both hovered and disabled, the browser falls back to source order. If the :hover rule comes last, the disabled button turns blue. If the [disabled] rule comes last, it stays gray. That sounds small, but it points to a bigger problem: component state in CSS often works by overlap. As long as a component has only one or two states, that overlap feels manageable. Once you add :hover , :active , disabled , dark mode, breakpoints, data attributes, container queries, and overrides, it stops feeling manageable very quickly. You are no longer just writing styles. You are maintaining a resolution system in your head. And that showed up not only as accidental conflicts, but as a growing difficulty in customizing existing components safely as real requirements piled up.…