I have not carried a quick link on a day ride near home, but I do carry a spare or two when bike touring. But then I am carrying a lot of spares and tools, etc. Seven years ago on a tour I had to dig out my cassette lock ring tool. But would never dream of carrying that sort of thing on a day ride.

Almost nobody has an S&S coupled bike, but one of my bikes has couplers. And one of the couplers started to loosen on a ride. I now carry a wrench to tighten them. But this is an issue for less than one percent of the biking population.