Becoming an atheist is not a choice. Those who really, desperately wish for there to be a fairy godmother to grant wishes, cannot conjure one up. No matter how hard they may try, those who wish to have a Santa or leprechaun, or even an angel cannot materialize one. They can, however, come to believe in one if they are able to have faith in such things. Not having faith can create an atheist, having faith can make one a believer.
A believer can have an experience that convinces them, wherein they sense the “presence” of a god. Sadly, not everyone can experience this. Those who do have such faith, are blessed indeed. They can always have the support, encouragement, and joy of knowing someone cares. This assumes the god they believe in is a benevolent one, of course.
People become atheists by skepticism.
It cannot be anything to do with want, as everyone would “choose” a loving God if given a choice. But skepticism is becoming more and more rampant as the global community becomes smaller and smaller. People are now well versed in at least the knowledge that foreign cultures have different faiths, even if they know nothing about them other than that.
This is a relatively new development. For the first several thousand years of human civilization, few people knew about the nearly four thousand different gods, goddesses, deities and belief systems that others had.
Also, before the advent of monotheism, people lived and belonged to a world in which they knew, and were connected. That changed when agriculture, then city-states, then patriarchy, and finally, the industrial revolution arrived.
After these things, all the interdependence that all faiths shared slowly faded away, to be replaced by the idea of “One truth only”. This would be alright if people did not squabble constantly about the terms of that one truth.
However, some indigenous cultures in remote pockets were able to maintain similar faiths in divine belonging sacred land, sky, waters and earth. But by the twentieth century, virtually all faiths of the earth became at least minimally aware of one another’s existence.
Assimilation allowed that people would exchange, blend and create ever new faiths that changed with changing values and scientific discoveries. Whereas these new values were often moral improvements, they shattered authority which allowed such ideas as man’s superiority or central place in the cosmos. They allowed, with Darwin and many since him, to learn that man is, after all, another organism; another animal that needs to live with fellow organisms to survive.
Some new discoveries ended things such as slavery, crucifixions and heretic burning, but they also allowed people to realize many different perspectives, views, and faiths of the world.
Faith is more dependable than reason
Atheism, then, is the modern inability for some people to be convinced that faith is more dependable than reason. No one knows by empirical evidence that this is so, or that there may (or may not!) be any reason to think people need faith as much as reason.
Atheism is not so great a threat as people fear if it comes to mean that humanity can embrace the divinity of the larger cosmos. When life forms become able to finally love one another and all life, including life beyond our species and our world, new earth of faith can be born.