I once set up someone’s computer. She is “tech-illiterate” as some call it (meaning she doesn’t know how stuff works or how to use it, except in the most basic sense of the word “use”). I enabled the “show file extensions” setting in the OS because I always do that when I set up a computer for myself.
So, instead of “Document Name” you get to see “Document Name.odt” or similar.
She then called me because she could not “save/open her office documents”… Turns out, she kept deleting all the file extensions, so the OS did not know what application to use to open them. The OS even warns you about deleting/changing extensions, I guess she just confirmed without reading/understanding.
Now I know why commercial systems for “end users” have this setting disabled by default… and now you know too. You just can’t trust end-users to not screw up. :D