A use case

Large Corp. is transporting a group of hard disks that contain important encrypted data to resort from point A to point B and in the transit, the HDDs get stolen. In this case, although the information is confidential (encrypted), now there is no availability.

If Large Corp. had taken care to copy the data of the HDD to a backup disk before transporting, then the availability of the data would have been maintained.

Availability can also be hampered by the loss of service due to man-made or natural disasters.