Can you further explain why raid/replication isn't a backup? Sure, you can't backup beyond what you've replicated (locally or across a network), but for most folks, that should be fine.
If you have a real business you need a multi-generational backup scheme of some kind.
Often, the need for a backup arises from the need to go "back in time". RAID and replication offer no solution for this. Ok, so depending upon your replication setup, it may offer some help, but the steps required to go back in time usually involve starting from a recent backup, and using files involved in the replication to "replay" recent changes to get you back to the moment in the past you wish to return to.