I had never considered the extended or "add on" warranty on any vehicle (or any other item I ever purchased). But.. when I bought my 2015 Yukon XL in 2015 and went from driving a 93 C3500 to the Yukon, the changes in the technology were truly night and Venus. Considering the factory bumper to bumper was 5 years and the extended was 8, I figured since it covered all of the electronics (and there are a LOT of electronics) and the mechanical, it was only about 1000 bucks. It was worth it. It's nice to have the peace of mind. Knowing (even now) that if I have an issue (such as last year my left brake light went out) I can call the dealer, drop the extended warranty and it's covered. We know the extended warranty doesn't cover paint, but what does? I still have another two years left on it, I suppose you could extend the warranty at the end, for a cost previously mentioned here, but it added three years of coverage and a number of miles, though I'll never max those out as my truck has 15,600 miles on it after 6 six years and it was more about the time frame. It was worth it.
I see there have been mechanical issues covered, and I figured the extra thousand bucks was worth that for the extra three years and covering all of the electrical stuff that can fail on these things, from screens to ignition and having those brake lights covered (which may have been just inside the factory warranty) but it may not have and when I took it to the dealer and they saw the extended warranty, they went ahead and replaced both rear brake lights, as they knew the left may develop the same problem as well.
I guess it comes down to your value and opinion, the extra three years for the extended 8 above the factory 5 is cheaper than dropping thousands for something small at 5 years and 3 months. Like any insurance, it feels like a "waste" of money until you need it.