One of the common answers is that it's driven by social demands and depends on the cultural expectation and the suggestibility of the individual.
I remember an example Spanos used to like to bring up regarding demonic possession. Catholics and protestants had different symptoms for demonic possession and people who exhibited it as a phenomenon each had the symptoms they were supposed to have. The long history of hypnosis, hypno-therapy and a variety of social and suggestibility related phenomenon suggests that's one potential cause for what you witness.
More recent theorizing talks about social emotional constructs such as social joy. The act of being with a group of people can make someone happy when all participating together and there is a strong feeling of shared belief. I think there's something to that and the general idea of spirituality that either comes from social contexts or strong isolation (isolation impacts an individual partly because of their reliance on the social). There is clearly some emotion that we can get that we attribute causally to God or a spirit that we do not fully understand. Of course, we've always attributed to God or a spirit that which we do not fully understand. Until we can better understand that and how it's important to the well being of humans, atheism will perpetually have an uphill battle.