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.