When I was growing up, my family went camping every summer - first in a large tent, then a pop-up trailer. We had lots of campfires, and we roasted lots of marshmallows. But we never ever made s'mores, and I didn't hear about them until many, many years later - probably sometime in the 1980's.
In the past 10 or 20 years or so, though, just having roasted marshmallows isn't enough. If you're hosting a campfire, you need to have the fixings for s'mores - marshmallows, graham crackers, and chocolate bars. The first written mention of s'mores was in 1925, in the "social section" of the Norwalk Hour. It was written as "some mores", though. It continued as mostly a tradition mostly limited to the Girl Scouts until the 1980's, when it really took off, and now we have veritable smorgasbord of s'more related items (I just couldn't resist!) - a Microwavable S'Mores Maker, numerous s'more cookbooks, and of course many s'more snacks, from pop tarts to cupcake mix.
How did it happen that a perfectly good special occasion treat - roasted marshmallows - became just an ingredient in another, even more special, treat?
I think it's a path followed in the past few hundred years by all luxuries, as the amount of wealth in the world has skyrocketed. First, an item is a luxury - a "gee-whiz", special occasion treat. Then, as we as a society become wealthier, it becomes more and more common. Until finally, we're surrounded by things that were previously special occasion treats. At that point, the item that's hardest to come by is self-control - to deny ourselves some of these extravagances that make us fat. And that's a serious problem, which cannot be solved by just throwing money at it.
As you might guess, I'm not a fan of s'mores - I'd rather have just regular roasted marshmallows any day.