A bigger reason is all the tooling for HTTP. Every language has libraries for HTTP. There are lots of proxy servers and application servers. It works in the bro

A bigger reason is all the tooling for HTTP. Every language has libraries for HTTP. There are lots of proxy servers and application servers. It works in the browser. It is all tested and reliable. Also, a lot of uses fit the request-response model of HTTP. Does it make sense to make new protocol or adapt HTTP when it can do the same thing? It makes more sense to focus on the application logic.