And if html allowed inserting html as it does css or js from external files, even that would be mostly be redundant. If only it let you use <html src="" /> at will.
https://blog.cloudflare.com/edge-side-includes-with-cloudfla...
Functionality should be considered based on potential utility. Not sure what politics are involved at the w3c, but if it's not that, then maybe it's their philosophy and approach that has them not going for that which is most useful.
Edit something, git commit/push, and within 30 seconds your changes are live everywhere. It's pretty awesome, and it requires no "server" hosting.
We are being simple, and I consider a simple PHP site about one step above HTML and CSS in required complexity, and about 5 steps below anything else in regards to tooling/setup/execution.