How can you unsubscribe from spam? If you didn't subscribe to it in the first place then no amount of pleading will make them stop and if you did subscribe then

How can you unsubscribe from spam? If you didn't subscribe to it in the first place then no amount of pleading will make them stop and if you did subscribe then it's not spam. The only things that help is aggressive filtering and and a good email client. Everything else is in the hands of sysadmins. I do not see the purported usefulness of this.