We have that. You can change contact info, set owner/technical/emergency contacts, alert thresholds, etc.
But unsubscribe means something totally different:
When I click on unsubscribe I want it to be the end of all communications. Period.
In this case, that makes no sense. Ceasing communications for all purposes implies service cancellation and, in our case, service cancellation implies a human interaction confirming data destruction.
How would we confirm data destruction for your implied cancellation if no further contact is permitted ?
You, and the blacklist operators, have become so jaded by the abuse you've suffered that you've forgotten that legitimate, paid services exist. I'm sorry.