Because cracked digests easier? I guess they don't have any problem digesting whole corn either. Around my parts whole corn is only .20c a bag cheaper than cracked, but I'm going by TSC prices. 50 # crack = $9.99.
So long as ample grit is provided my birds can handle digesting the whole kernels even as three week old chicks so long as they don't get too much. I get a fair portion of my feeds through TSC as well although not always cheapest option which is where price difference is as I see it. I have been getting cheaper whole corn (usually depending on market price) from our local farmers coop. We up here are much closer to corn-belt so that may impact price differences as well.