Plans change fast in this business. A show gets rescheduled, a presale sells out early, an artist drops off the bill, and whatever campaign was built around the old plan needs to stop moving right now, not after the next send window fires.
Pause and cancel gives you a direct way to stop a running campaign without tearing apart the automation you built. Pause it when the hold is soft or the change might be temporary. Cancel it when the show is off for good. Either way, the campaign stops touching your list the moment you need it to.