Why can't HTML some kind of templating system, or even simple includes? Then I wouldn't need to use a static generator and could just author HTML directly.

e.g. (with hypothetical <extends> and <block> tags)

template.html

    <!doctype html>
    <html>
        <h1>My Fancy Blog</h1>
        <block main/>
    </html>

index.html

    <extends "template.html">
    <block main>
        <body>
            Hello world
        </body>
    </block>

Maybe this would compromise browser performance or add some kind of vulnerability, but authoring DRY HTML directly is my fantasy