While we could make it so that clicking the link in your email would immeadiatly unsubcribe you, it would be in violation of internet standards. Insbesondere die Definition der __GET-Methode__ des __HTTP__ Protokolls, die besagt, dass:
Eine _GET-Anfrage_ ist das, was passiert, wenn du einem Link folgst. Merely following a link should not make any changes (like unsubscribing you from a newsletter).
For example, when you receive an email, your email client may _preload_ the links in it in the background. So that they are quicker to load should you click on them.
Obviously, this preloading should not unsubscribe you. Which is why you need to click a button to confirm. Because that will trigger a __POST request__ and those can make changes.