Earlier quoted context omitted.
You'd be surprised for how many technology-inept users that wouldn't make a difference. They'll still mark the email as spam. It's easier for many people to understand and easier to click.
It sometimes can be better to mark it as spam. There was a thing a while back where the unsubscribe link was just verifying that you still check that email account, and you click on links, so they'd send you more spam.
Senders who bought, stole, or brute-forced your email address are a different story. For them it's just a numbers game. They are, by definition, spammers and should be treated as such.
There is a final group of senders who you did once interact with but who show these behaviors:
1. They are too incompetent to keep the unsubscribe server running;
2. They broke the the mail template so it doesn't point to a valid URL;
3. They fail to control subscription preferences within their own company so that the marketing department keeps using the same old list even though months of unsubscription requests have accrued since then;
4. (My pet peeve) They take you to a blank form that asks for personally identifying information in order to unsubscribe, rather than embedding an identifying token in the email's unsubscribe link. Out of principle, I will not enter PII into any form on the other side of an email link, even if it comes from someone in my family. It's too easy to fall victim to phishing, and I resent any sender that puts me in that situation. If a business asks for any PII to unsubscribe, I close the tab and mark the email as spam.
Any of those get marked as spam. Their intent was not to spam me, but I can't do business with incompetent senders.