You can understand their purpose if you read all of them, and even moreso if you do them.
They are designed in private by the Clergy with the guidance of the Gods.
Each Ritual is meant to establish who the God truly is, remove slander and expose you to the original nature of that God and the things the God represents in their purest form. They also honor the God, help you connect to them in a more official way, and exposure to the Gods in this way develops one's soul.
The God Power Rituals represent the best, easiest, most accurate way to develop a real relationship with the Gods. They will open many doors.