That's why I suggested looking further back. The medieval era, as gozer88 said, the priests were the only literate people to transmit orders and record things. They also got to define history... significant amounts of historical and contemporary knowledge at that time was always filtered through the lens of the catholic church.

Zip ahead to US colonization. Why did people come to North America? In many, if not most cases it was to escape religious prosecution or the blowback relating to that persecution.