“If every feature required a specific header to signal that it is unwanted, that would get irritating rather rapidly.”
Outlook lets users tap a thumbs-up on an email. Everyone outside Microsoft’s system gets a whole new email saying “[person] reacted to your message.” The fix is a header called x-ms-reactions: disallow that every sender has to add to every outgoing message. Microsoft invented the noise and made the rest of the internet opt out of it.