They spread the load out more evenly and provide friction in a larger area than just the bolt / screw. They can also provide expansion to prevent the eventual loosening due to movement (lock washers).

I apologize for the dupe. I did my best to try and find if someone posted it, but I only have time to keyword search, watch the top 15, and rely on the dupe check process during submission. it seems had I come to the party two hours later i would have seen your submission.

Is there any value in using the YouTube from mine as a backup?

Otherwise, what is the etiquette? Should I discard mine or kill mine?