Virtual Chicken: The Ceca

The ceca are two blind pouches located where the small and large intestines join. Some of the water remaining in the digested material is reabsorbed here. Additionally, any remaining course materials are broken down in the ceca through fermentation. During this fermentation process, the bacteria in the ceca produce several fatty acids as well as the eight B vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid, and vitamin B12). Because the ceca are located so close to the end of the digestive tract, however, few of those produced nutrients are absorbed and available to the chicken.
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is there any known reason why it did not evolved to absorb those nutrients from the ceca? Or it absorbs just enough and the rest is not needed?