In addition to some other points. Spam detection systems that email providers use employ a scoring system. For each element of an email that is associated with spam the score goes up. For each element that is associated with legitimate email the score goes down. Things like including a real physical address of the sender’s company, phone numbers, etc are associated with legitimate email. Having a legitimate unsubscribe link helps convenience the spam filter software that the email is legitimate and increases the likelihood that it gets delivered. The vast, vast majority of all email is spam and is blocked outright. Only the “well crafted” spam gets through to your inbox.