The pigs declare Moses’ stories about Sugarcandy Mountain to be lies. Yet they let him stay on the farm without working, and they give him a daily ration of beer. Why do you think they allow him to stay and even give him luxuries?

Perhaps having a talking raven around isn't such a bad thing after all. The Pigs keep Moses around to convince the animals that if they just work harder, there are a paradise that waits for them. Linking the state with "religion " or mythic belief has its benefits.