Lunabella has obligations to respond to Outsider issues. Some of these are expressed in the Iron Tablets. Others of these are expressed nowhere public, are in no way magically binding, and don't have formal consequences if broken.
Lunabella cares deeply about informal consequences to pride and security, and isn't subtle about it. The general expectation among emergency responders is that if a Lunabellan team is supposed to show and doesn't, Lunabella is probably itself under attack.