RAID is really about availability. The idea is, with RAID, you're protecting against device failure, drive failure, component failure or a failure to be able to access that storage. Other data protection techniques, whether it's backups, snapshot, replication, getting a copy of the data as of a particular point in time is necessary to complement RAID.
RAID protects your data, so if a drive fails you can continue to access it. If all your drives fail, where are you going to recover data from? To protect yourself to a particular recovery point objective [RPO] and recovery time objective [RTO], you still need to combine RAID and backup.
Check out the entire RAID FAQ guide.
This is something that's been talked about for quite a while.