How does that work anyway? If you decline to allow the site to store a cookie on your machine, how does the site know that you already rejected the popup to avoid showing it to you on your next action?
If the permissions were managed by the browser then cookies could be managed directly on the client side without server side interference, and preferences could be communicated to the website via headers (like DNT but GDPR requires a lot more granularity, and is also legally enforceable in the EU).