Think about it this way, most developers should have been familiar with CSS, utility classes is a shorthand that make its easy to remember and find user defined class if you have tried Tailwind 3, I found it solve all of my checklists.

Like Bootstrap way, you can still define that with Tailwind classes either in input.css with @apply directive (abstract out utility classes from HTML) or Tailwind configuration. It’s a way to speed up our development.