Religion

In most times and places throughout history, people have worshipped one or more of what they thought were superior, supernatural beings.

It may be that the reason for this is that people have felt that there was some level of existence higher than their own, and have sought to explain this in the best ways that they could.

It may also be that there is a continuing desire for a parent even in adulthood, which has led people to create a "super parent" to fill that need.

I suspect that the presence of religion in almost all (if not all) cultures, is due to a combination of these two factors.