Even more to that point we only need HTML (in any flavor) because the browser says we do. The compile target is the DOM. The DOM is the goal, not HTML. If the environment were treated more like WASM where any language could compile to the target then it wouldn't matter what the source language is.
I imagine rendering a website to be much faster if the initial render is just streaming bytes from the network into the browser runtime, instead of parsing some string.
Does it really matter? The data representation could be markdown, yaml, JSON, SVG, or just about anything else and be equally effective. The browser already supports XML and HTML5 as wildly differing grammars that still compile to the same target.
html is not a DATA representation, it's not designed that way and it would actually be way more noisy if attemps to represent all the hidden states of the DOM.
