Maintainers get requests to do things they have no interest in, like maintaining software for OSes past a certain date. That doesn’t sound so bad, but there are a lot, and they can even be mean. The maintainer can block these users individually, but it’s different users all the time, so that doesn’t stop it.
So, the maintainer addresses the user base, the whole crowd all at once. The problem is most of these users haven’t seen these interactions, so the message seems hostile. Having someone say “I owe you nothing.” seems really weird when you’ve never asked them for anything. Or, if they list of all the ways and reasons for you to not contact them it looks hostile. The users don’t see the fan next to them throwing a beer can at the center fielder.