This happened to the entire US federal government in 2014. Someone reply-all'd a mailing from the General Fund Enterprise Business System notification asking to be taken off the list, and it escalated as then thousands of people who didn't realize they were on this list did the same thing, then got worse when smart asses reply-all'd telling other people not to reply-all.
Part of the problem is from admins creating lists and putting users on them without user knowing anything about it. Can you blame users for being confused and seeking to get off a list in the only way they know how? IT Admins bare blame in these incidents. The users just make it fun for everyone but IT, but IT hopefully sees the fun later when they aren't running around putting out the fire
May I amend this to say "IT policies" are to blame?
Thinking back to my own days in the IT Department, I would have LOVED to say "No" to the requests to make yet another distribution list for a Senior Manager or Director, full of everyone and their assistants for the very same reason as you (plus a few other reasons), but that was just one of the many things I had a lot of power to execute but next to no power to actually influence-at least if I had any expectation of keeping my job and not getting chewed out for balking at such requests.
Memory goes back to the two worst IT Admin positions I held, both were in high volume calling environments, both involved people constantly moving between teams, managers renaming teams, trading personnel, moving people between groups, hot desking--all of which involved the constant creation and distruction of distribution groups, ring groups, hunt groups etcetera in ADUC, hot phones, not to mention the nesting of groups within groups within groups, and no amount of "showing my work" to the Director or IT Management to show how nothing was getting done except beating our Exchange Server into a bloody mess got any movement from anyone in leadership
