Andrew Stuttaford, a non-believer, describes why so many children of the non-religious turn into theists:
Belief in a deity (or deities), and the desire to worship it or them, is an almost universal aspect of human nature. This not something that can be wished or indoctrinated away, and it’s pointless and maybe even destructive to try. It’s far better, surely, to channel that impulse by giving children some sort of gentle religious grounding, preferably in a well-established, undemanding, culturally useful (understanding all that art and so on) and mildly (small c) conservative denomination that doesn’t dwell too much on the supernatural and keeps both ritual and philosophical speculation in their proper place. Better the vicar than Wicca, say I.