Kodak Disc occupied the ecological niche of the 110 format: a camera which could be always in a woman's purse, to capture moments of her children, school parties, holidays, happy hours with friends etc. Good for having always with you, just in case. Probably 126 had the same intentions initially, but the cameras were not small enough.
126 had the advantage of the light-tight cartridge in respect to 135 which requires you to learn to load a film into the camera. That might seem trivial, but I remember, when I was a child, my parents going to the photolab, or to the photo shop, with the camera (Voigtländer Vito C) to have it unloaded and loaded. As easy as it is, some people just fear complications. 126 was brilliant, because you would be "dead sure" that you could load and unload your camera without risking the film to catch light. At 7 years of age I could load my Kodak Instamatic, and they couldn't load their serious camera (!).