I think they changed the formula of Iams a while back at about the same time it started appearing in supermarkets. I used to feed Iams dry when Jaffa was little (years ago, before I knew about the cruelty thing). I think a lot of the dry foods have oils and fatty acids added to produce glossy coats but that doesn't mean it's a healthy food or that the cat is necessarily healthy inside. I do think that we are victim to the same thing with pets as we are with human hair - thinking the hyper glossy look = healthy. Good hair condition (whether it be humans or cats) is equated with good health but the super sleek, shiny look that we tend to expect these days is often achieved artificially and a bit fake imo. I can get my hair looking really shiny if I use the right products but I eat rubbish and am probably not very healthy inside
Having said that, Mosi has pretty shiny fur but I think that's because he's young and healthy and eats a good diet in general. Jaffa's is less shiny but it's a bit lighter than Mosi's so doesnt' reflect the light so well and he's older. It's pretty good when he's taking a viacutin capusle each day.