I think that indoctrination is a common cause of belief. However, at what point does that translate into a spiritual desire for peace or wholeness? I feel as if indoctrination often does the opposite, but it can provide a set of rules to obtain peace, many of which are often misleading.
I tend to agree that people are searching to feel a wholeness or "completeness" in their life and that many people feel a figurative hole in themselves. I Still believe that this "hole" revolves around the unknown aspects of life , and the desire to accept an answer without question. People find all different ways to do this, but I believe the desire for it is a result of most of the human races biological need to have an answer, be it true or untrue. For an atheist the answer is that we are just organic matter, it is a very definite answer to many elements of the unknown.
I take the stance that there may, or may not be a God. What is more important and provable to me is that there is organized energy in the universe. I certainly don't believe that ANY of organized religion has hit the nail on the head. Spirituality is a part of humanity. Organized religion is made mainly to give others authority "above all" and develop an infrastructure within a group of people. It sickens me to look at the length it has been defended by different groups over time.