Hacker News is very much a collection of documents and forms with hyperlinks creating the whole concept of applications. No need to add desktop interactivity (which is already provided by the browser: loading documents, submit the form,...).

Most SPAs are reinventing the browser features (history, routing, navigation state, submitting forms, showing request's responses). When you really needs a full fledged application, those don't really matter (Figma, music players, document viewers,..).