Candy Bars of Yore

I'd like to know what led to the demise of The Chunky Bar. Was it just an 80's fad like Tab Cola and Geraldine Ferraro?

And furthermore, why do candy bars periodically have to have their recipes changed? I remember, as a young lad working as a bootblack in the streets of London, (OK, I made that part up) the candy bar Wathchamacallit had its ingredients changed, or reformulated, as Hershey's calls it. This ended my era of Wathchamacallit enjoyment. Now I suppose if you're already making a candy bar called Wathchamacallit that probably gives you license to throw whatever the hell kind of ingredients you want in there, but to me it just wasn't the same.
Maybe I'm just an old man ranting about the way things used to be and upset over today's new fangled snack food items. But more importantly, I'd like someone to tell me what "fangled" means.