3. Protect against accidental deletion
Mistakes happen. Even with the best training, your employees are only human, and unfortunately, human error is inevitable. If somebody accidentally loses, deletes, or corrupts a file, or any other important piece of information, a backup may be recovered. A 365 backup also protects against mistakes made by administrators, not that it ever happens! One of the most common examples being the deletion of a user, which is then replicated against the entire network.