As with all things, it's a double-edged sword.
While I would never disdain backups for protecting data the backup itself introduces more attack surface, and potentially an unguarded one, or at least one that isn't normally given much thought.
Typically, there are multiple backups, previous versions, if you will. If the last one's corrupted, fall back to the one before, and so on.
Solid strategy, but a backup is still a copy of the data. While your database might bristle with all manner of defenses, some of them active and aggressive, how many defenses does your backup have?