since it's higher in carbs, so it helps them have enough to generate a bit more heat.
Higher in carbs than what? Or is it just lower in protein?

Carbs and protein have the same amount of calories per gram. But NOT the same amount of vitamins, minerals, and amino acids. If someone wants more calories on board for available energy seems like fat would work better than carbs.
To me scratch is an added expense. I don't think the chickens are being deprived of anything any more than a baby not getting a slice of cake. If they don't know it they don't care. It's nice to have a treat once in a while though, I'm sure. But there are lots of enrichment options... like hanging a head of broccoli just out of reach or an ear of corn. But as stated by jreardon, calling them in and getting them to scratch around and those type of reasons are understandably good. When used correctly, it shouldn't be a problem. And chickens sure do seem to be crazy for it! So I hear... since I haven't bought it 9 years of keeping chickens. I'm a tightwad when it comes to health!
I like to feed back extra scrambled eggs, or chopped corn tortillas from the bag we didn't finish. Live meal worms. I just don't need an extra 50# bag of something sitting around waiting for months to be fed out and diminishing even further it's nutrient content by age.
I far prefer to sprout barley or wheat or anything really. Sometimes even grow it out into fodder for rainy days. Sprouting is a GREAT way to get some greens in the diet, so easy to do, and highly enjoyed by chickens in addition to being a decent source of nutrients at about 14% protein. I think peas come in at 22%. And turn around in as little as 4-8 days.
