The Real World Zombes

In haytian folklore, a zambi is a dead person who has been brought back to life through folk magic. They are then used to perform manual labor that doesn't require a lot of skill or dexterity. Anthropologists and medical doctors have studied them. This is not an april fool's episode. This is real. And in case people are wondering, i am not kidding. The question is, what explains this sociological phenomenon?