Religion is not necessary for everyone (I didn't mean that). Some people are fine without any form of religion and that's ok. But statistically and historically and perhaps etnographically speaking, majority of cultures have religion and this coutinues though thousands of years. There is margin for all kind of enforcement, pressure, etc, but anyway what's left is really a phenomenon (the volunteer believers). It's a product of evolution, IMO. That's why I think religion must fill important **primary human needs**, otherwise it would not persist till computer age. I think it will be the same in a hundred years, as long as humanity will exist.
You've changed the goalposts, to "volunteer believers", and undermined your original post.
Volunteers believers are the hippies that have taken DMT, which is a purified form of Ayahuasca, which is used in South American ritual. The people consume it and have big galactic visions. They had the visions themselves, so the drug has told them that spirits really do exist. So, you could say they were volunteer believers, who now have the idea that there is something that transcends consciousness, (a) because they think they experienced it (b) because they need life after death, and some point to live.
However, it's not strictly volunteering, if the drug is just a delusion. It's an ancient religious culture which got thrust upon them. It would be volunteering, if there was any truth to it.
You could argue that some religions do not really fill a need, because they are designed primarily to spread effectively, rather than consider a human's evolutionary need. So, there is a "spread" component, and a "need" component in religion. In the case of Ayahuasca, it's a very powerful cultural method of spreading belief, by demonstration. And, it also seems to fulfil the vague artistic "needs", by giving lots of wonder, and no firm dogma.
In the case of Christianity and Islam: these two dogmatic religions seem to be the least spiritually artistic, and are dependent upon state orthodoxy and threats. (Without state backing, they would degenerate badly, into something a bit more artistic.) The Christian ideal is to be celibate, living in a closet, while flagellating yourself, attempting to avoid burning in hell for eternity. You may stare at stained glass windows, as long as they have pictures of cherubs, and a man dying on a stick. Christianity lacks so much spiritual art, that adherents have no real thought as to what could happen in afterlife. While denying themselves in this life, they have no visions of why they would bother going to the next one. Islam is also very vague about why you would want to hang around with rivers of wine, but it is pretty clear about how we should treat women.
You could say that the point of the atheist argument, is to help people who have had religion thrust upon them, by its unartistic spread and threat component, to create more people who have volunteer beliefs.
Another way of looking at it, is that Christianity and Islam have evolved to build empires. If the empire builds, then it does not care how it treats its people. But, in order to build an empire, it must treat people relatively well. However, the way they are being treated is not necessarily what they need to believe evolutionarily as a person. For example, I have no need to believe that I will burn in hell, if I think about my neighbour's wife. It may keep civilization more on track, if I don't think about my neighbour's wife, but it has nothing to do with my personal needs.
In teaching others to think for themselves, it could well fill an evolutionary need, but may also weaken the civilization, and render it vulnerable to another dominating religious culture. This is the problem with atheism: it may be only transitory, before we move into another religious prison.