Each generation seems to invent something new, so there should be little surprise that the world is covered with different denominations among religions. While this is true, many of the oldest religious beliefs and practices are still flourishing today. They have not survived due to any deep mystical source, and forced practice of any particular beliefs has long been banished in many parts of the world. What keeps people passing down their religion to their children is discovering the continuity in religion as they age.
The goal of many faiths is to help their members throughout life, and they have rituals to cover almost every important step. Getting baptized as a baby or even as an adult is one of the big steps that have been passed down through generations, and it is often followed by being accepted as an adult in the same religion. This is called Confirmation in many religions, and it is generally followed by the ritual of marriage.
For those who are founding in their religion, their early years as an adult are often a time when they turn away. They might simply drop out of their church as they enjoy other aspects of life, or they could turn away due to a particular incident. When they feel there is something missing in their life is when they embark upon the adventure of having their own family, and this is a time when many of them turn back to their faith.
Children are often a blessing for their parents, but their advent can make them question their own lifestyles. Those who turn back to their former religion have often found they want to pass on the traditional rituals to their children, and they look forward to the steps they will take as they become adults too. It is this continuity that has given life and longevity to many ancient faiths even today.