Ask HN: Standard renderable webpage archive format?

Why don't we have a simple archive format for offline html and its assets that can be rendered in browsers? We're stuck with PDF's which are a nightmare to impliment software for, and most of what PDF's can do can be done in a webpage it seems.

For example what about just a tar file that contains the navigated pages .html, and the assets for it (images, js, css, etc) which simply treats it like a local file in the same folder.

That's make it possible to easily use archive software to access the assets, and still be able to render the page in browsers.

Currently we have mhtml, which inlines assets, and we have HAR which is unsafe because of cookies, but again inlines assets, and only mhtml is renderable in chromium or internet explorer.