Religion, especially the hope of a paradise waiting after death was a powerful thing to a slave population.

Until very recent times, even those people not in chains were enslaved by their environment. They spent most every waking moment tending their flocks, gathering herbs and roots, or hunting meat. As soon as they could walk at their Mother's side, they began helping in the gathering of food. Or the little ones took their dogs and tended flocks and chased away predators.

Religion and the thought of Heaven gave them hope of some reward after their unending suffering with labor, hunger, pestilence and early death.

Today, in developed nations, there is much less need for such. It is a natural progression, just as is the move toward smaller families.

People who choose to brew up their own storms bitch loudest about the rain.