I'm all for screen protectors as extra insurance against small bumps, nicks, and randomness. The good ones barely take anything away from the display, don't cost much, and help to preserve resale value as others have noted.
PowrDroid, I didn't realize you posted the video here as well before I responded in that other thread first. I'm putting the bulk of my response here since the topic is more applicable. At 7:23 of your video, a bunch of scratches on the screen are shown.
There's no argument that Gorilla Glass 3 does a very good job in reducing the likelihood of scratches, marks, and cracks. But not to the point where there's no reason for a screen protector. This doesn't directly translate to "no screen protector = scratches galore", but to me it's not worth risking it when there's something available that barely affects user experience, if at all. On the other hand, if the naked screen happens to get scratched, that would definitely affect my user experience.
I can also make PowrDroid's claim that I've never had a damaged screen surface either after always using screen protectors. I'm glad it's worked out for your naked screen - but it's an n of 1. There's quite a few reports online of people with Gorilla Glass 3 scratches after regular use, more so from sand than anything else. On the other hand, there's very very few reports online of anyone having scratched any Gorilla Glass screen that has had a protector on it - I can't say 0 because I haven't been to every website, but I couldn't find any coming from regular use. Sand hasn't affected my screen or the protector the multiple times I've had my phones with me on the beach or camping. A screen protector isn't the be-all-end-all, but it doesn't hurt and may just help.
I have a link to show also - this is how the Gorilla Glass marketing director himself talked about the product... good improvements for scratches, but doesn't say anything about them not being an issue anymore:
Gorilla Glass 3 promises 40% fewer scratches | Computerworld
There has to be room for improvement for our Gorilla Glass 3 screens, because Corning is currently touting Gorilla Glass 4, which their website says is 2 times tougher than anything else out there and that it survives drops "80% of the time". Really good, but we're still many years away from "practically indestructible", as was claimed in a different thread.