I can only guess you have yet to suffer the usual failures so let's skip all the RAID discussion and head for the answer.
1. It's still not reliable enough to not backup to the 2 to 3 copies and have a copy off location.
2. It never saves folk from the most common delete the file/folder oops sorry boss gaffe.
3. This has never saved any company I know ONE DIME. They pay the same price if they didn't backup.
On a Wintel PC, are single internal hard drives considered reliable enough that drives in RAID 1 configuration are considered redundant these days? I'm debating whether to get a 256 GB SSD & 1 TB Raid or a 256 GB SSD and a single 1 TB HD. Obviously, the 2nd option would save some cash that could be spent on other components.