Of gods and kings
Religions primarily serve as a psychological conditioning model of the hierarchy of power. There is the god-king (patriarch), followed by his angels and disciples (members of court, politicians and public servants); and of course, the saints and sinners -- the obedient subservients pitted against the non-believers (creative-types and non-conformists).

The flock of followers are kept in line through a system of fear and reward. Historically, there has been much to fear. From the Crusades and the Inquisitions to the Conquistadors and colonialism, people the world over have been slaughtered and enslaved -- their land and resources stolen -- all in the name of religion. On the other hand, the rewards of 'conversion' have to be taken solely on faith -- the belief in something that cannot be proven -- how convenient.