I suggest reading the introduction to either of these specs:

- https://datatracker.ietf.org/doc/html/draft-toomim-braid

- https://datatracker.ietf.org/doc/html/draft-toomim-httpbis-b...

People do synchronize at the application level today. But every application invents its own non-standard synchronization method, which is incompatible with every other application. This results in each website only accessing its own state, rather than sharing state with other websites, and the web becomes a bunch of walled gardens.

In order to decentralize the web, we need a standard for the internal state of websites, that makes it easy for websites to re-use the state of other websites. Where the original web allows any website's pages to link to any other site's pages, Braid allows any site's internal state to synchronize with the internal state from any other site.

Now, you might ask why we should implement a standard at the HTTP level, rather than make a standard on top?

Well, it turns out that HTTP and REST are already designed for sharing state-- but they are just limited to state transfer rather than state synchronization. It is very natural to extend it to synchronization -- we can do it with just 5 new headers, 1 new response code, 2 range units, and 1 new registry.

And if you try to build something on top, you'll have to re-implement all the great things that HTTP has invented that we now take for granted: caching, CDNs, idempotency, media types, etc. By putting synchronization into HTTP, we can add these features to the existing web. Caches (like CDNs) can suddenly support dynamic content -- not just static content. If you change a line of code in your Javascript, all clients will update with just a diff, rather than re-requesting the entire file. The reload button becomes obsolete. Existing HTTP network traffic becomes more efficient. Every TEXTAREA can become a collaborative editor.