For people who move from religion to atheism, some have learned to maintain the internal belief structure, and fill it with new contents. By that I mean, if they were raised in a dogmatic religion with absolutes, then their atheism will tend to be dogmatic with absolutes. If their religion was a closed system of thought, then their atheism can be a closed system of thought.
What religion, and more specifically - spirituality, can teach people is that there is more to the universe than the concrete, observable, and measurable. There isn't any reason to think that the human mind perceives the whole of reality through the concrete senses. In this way it can teach the atheist a sense of wonder, mystery, and speculation about the possibilities of reality.