ZFS has RAIDZ1, RAIDZ2, RAIDz3 and Ditto blocks, which do much the same thing, although a bit differently.

My point was that even if you have 4 copies of your data, you still only have a single machine where your data is stored, and you're essentially just one flood/lightning strike/house fire/burglary away from all of it being gone. Or one bad power supply away from 4 dead drives.

With versioned backups, you have higher latency on restoring data in case a disk dies, but your data is also safer.

As i initially stated, RAID is for availability. It is great for making sure that data is available 24/7, but that is rarely what the average home user needs. Most home users access their data infrequently, and would be perfectly fine waiting a couple of hours while restoring data from a backup.