Why on other sites where they were implemented on React is the page loading through a reload?

Question

JavaScript

Good evening, I noticed one feature even in facebook itself. When you open any page - reload. Why is this being done?
I use react-router-dom, configured routers and components. Now when you click on the link, the page opens. There is no reboot. Then I realized that my site was made according to the SPA principle. I don’t know why React sites reload pages at all, but it seems to be done like this:
on NodeJs through handlebars.js, I create pages, then I make api and load these pages at these addresses? I'm trying to figure it out, but I don't know how to make a NodeJs + Express + React stack (not a simple SPA)
I can do a regular SPA, through webpack, I collect everything, link backend (express) and access index.html. So you can make a big site? Explain to a newbie :)

Answer 1

You can, you just need to use webpack code splitting.
You will also have to figure out caching of already rendered pages, data caching (apollo will help with this for graphql, and there is something similar for rest), and unloading excess from memory.

Answer 2

Everything is simpler, the same Facebook is not made on React, but only uses it in places.