That is to give the spammers your new address on mail that's forwarded from an Bld and possibly expiring one.
Back in 1998, when I was putting my company on the internet, I received a spam on my regular address. I created a new fake user, and opted out with it. Within a day, it was receiving spam. Over the following week, its level of spam reached that sent to my own. One opt out was the only way anyone in the world except me could possibly have known about the existence of 5l1ckw1lly@kingsystems.com. I tried a few others after that in case the one I chose was a "bad apple". The other usernames were less clever and I don't remember them, but they all got the same result.
Honestly, there were so many duplicates of my experiment (it was 11 years ago - I was probably a duplicator, not an originator) that it's surprising to me to see this question even asked. Spammers know you don't want to hear what they're saying. They try to fool you into reading it, like a tranny trying to fool you into letting it... well, just ask that Anrade idiot. What makes you think anything else they say or do is trustworthy? I wouldn't trust a spammer I saw crossing the street to actually be there when I ran over him.