If you[he]#039[/he]re on an email discussion group long enough, at some point, you[he]#039[/he]ll see an email from a list member asking to be unsubscribed. Typically, at least 10 other people on the list will respond with instructions on how to unsubscribe, and those 10 responses will be answered by 10 more people confirming or commenting on the instructions. That[he]#039[/he]s a lot of traffic to a mailing list just so one person can unsubscribe.

Source: LXer – How to conveniently unsubscribe from a mailing list