A backup you haven't restored isn't a backup, it's a hope
Backups fail silently more often than people expect. A job that "completes" doesn't guarantee the data is actually recoverable.
Most backup software is very good at reporting success. A green tick, a "backup completed" email, a dashboard that says everything's fine. What it's usually not as good at is guaranteeing that what got backed up can actually be put back — those are two different things, and the gap between them is where a lot of businesses get an unpleasant surprise.
Corrupted files, incomplete backups of a database mid-write, permissions that don't carry over, or simply backing up the wrong folder for months without anyone noticing — none of these show up as a failure in the backup log. They only show up when someone actually needs to restore something.
The fix is unglamorous: periodically restore something from the backup and check it opens properly. Not the whole system necessarily — even restoring a single file or folder and confirming it's intact tells you the pipeline actually works, rather than just running.
If you couldn't say with confidence when your backups were last tested by an actual restore, that's worth changing before you need to find out the hard way.