You probably got removed from the list because it cost someone a stamp to mail you the letter. These days if you respond to anything, that just puts you on the

You probably got removed from the list because it cost someone a stamp to mail you the letter. These days if you respond to anything, that just puts you on the 'real person' list that gets distributed to all the spammers. Email and robocalls are essentially free so there is no incentive to take dead ends off the lists anymore.