Not My Job
It’s a toxic statement. One that is used in a righteous posture, but always comes with a sting of indifference. Yes, that thing someone has asked you to do may not be your responsibility, but that doesn’t mean you shouldn’t do it.
Protecting your time and sanity is important, and saying yes to everything is unreasonable, but there is something to be said for going out of your way to help a coworker or friend.