Because your not thinking of styles practically. You don't review style declarations, you review the rendered page/component. You see with your eyes that a component has the wrong border color, and AFTER THAT you go to your component code, find the border color declaration (if any), and update it/add it. Sometimes you'll even inspect the element in browser, and find the faulty class directly, making it even easier to target in code.
The Tailwind classes are "unreadable crap", that's true, but it's not a problem because you don't "read" it, no one does. You roughly parse it and edit it.