Reusable code. General functions can be shared between client and server code.
Fast initial page load. Server has rendered initial load of Single Page App into HTML and is ready to be rendered by the browser. The browser does not need to execute bundle.js to draw and mount our SPA to the DOM.
SEO benefits. Serving pre-rendered HTML allows search engine crawlers to crawl and index our website.
Source Code: Server Rendered vs Client Rendered App.