That's the goal. It used to be that JavaScript and web development was very difficult because the languages were lacking. Today the languages aren't lacking but there's still a psychosis that won't go away. React was built for extremely complex websites like Facebook, specifically for Facebook. And now people use it just to make buttons or range sliders. Or to develop a blog, or an about page.

Despite the fact that you can make a button or a range slider natively in HTML and CSS which would be much more performant with a smaller footprint on both bandwidth and cpu. What can you say; ever since jQuery everyone has been dying to reinvent HTML and CSS, it's exactly what you just pointed out.

They're well-styled widgets that are composable and easy to integrate into client code without adding a bunch of dependencies (like globally-defined CSS classes). What's not to love?