Think of tailwindcss an html-level "API" to a Design System - it provides a consistent color scheme, consistent padding/spacing, it uses a familiar naming scheme that aligns closely with the the original CSS naming. It's also easy enough to extend with your own customizations as well, particularly once you get a grasp on the advantages of atomic CSS [0].
[0] https://johnpolacek.github.io/the-case-for-atomic-css/