This is how I interpreted the original question and indeed it makes no sense, JavaScript from a website should not be allowed to interact with extensions like this.

Chrome exposes these files via a URL that you can fetch in javascript like you would any other file on a normal website. These local extension files usually contain code, styles or images that your browser needs to run the extensions.

Because extensions can and often do contain stuff like images or JS bundles that they inject into a target page's DOM. Not allowing a tab's context to load files from the chrome-extension:// namespace would break a lot of things.