This advice doesn't seem to be getting through regardless of how loudly it is proclaimed. Everyone should have a backup plan with multiple points of failure, but of course lots of people don't because it's not trivial to set that up.

I don't think current operating systems go anywhere near far enough in helping users to get this right. When I buy a computer, the computer should be in charge of ensuring that catastrophic data loss cannot easily occur. 9 times out of 10, the user simply doesn't know how to set things up that way.