Take addons.mozilla.org. It's a simple, tiny website with a list of browser addons and a button to download each one. Perfect fit for server-rendered HTML, right? Nah, front-end developers rewrote it in React. [1]
Or blogs. Blogs are just a collection of text pages with occasional images and links. Surely you should use static HTML for those, right? Well, okay, but only for the initial page load; after that, make sure you let React take over so it can "improve" your page navigation. [2]
[1] https://blog.mozilla.org/addons/2017/10/25/test-new-look-add...
[2] https://www.gatsbyjs.org/blog/2017-07-19-creating-a-blog-wit...