RFC 8058, published in January 2017 by the IETF (Internet Engineering Task Force, the body that writes internet standards), describes how a sender signals a one-click unsubscribe in the List-Unsubscribe email header.
The stated reason is that mail software sometimes fetches web addresses found in message headers, which can cancel a subscription by accident. A newsletter that follows the standard lets readers leave with one click in their mail program, and an accidental fetch cannot unsubscribe them. This is synthetic content for checking the email path, not news.