You want to avoid duplication, usually. You can also do it by creating components in React (and other frameworks). Doing so keeps the style close to the component definition which I think is good: if your component is say a nav bar some of its appearance comes from how you nest flexboxes and some from the flexbox configuration. Why not keep that all together?

Isn't this the very point of tailwind? If you don't like it maybe just don't use tailwind.

So what is the point of using Tailwind if you do not want to use its main feature?