I remember reading an article not long ago in the New York Times that talked about how most young people these days are neither atheist nor religious, but consider themselves spiritual. If we're talking strictly about religion then yes, people who are not indoctrinated from an early age tend to not subscribe to religion later on. There are exceptions of course. Some people end up gravitating to religion for various reasons. I notice that a lot of people who hit rock bottom end up converting to some kind of faith-based system in adulthood because they need to build a spiritual core in order to move forward (since they lacked it in childhood). A friend of mine who hit rock bottom as an alcoholic joined AA and then later became a born-again.
But I mean... most people don't end up doing that. With a critical mind and open heart, it's actually not that big of an accomplishment to let go of belief in various narratives, like religion or whatever else the institutions taught us growing up. They're all just stories that we can attach to (or not) and use to develop a relationship with reality. It takes a much more discerning consciousness to dive into an interrogation of reality, parse it, and come up with one's own answers. It is its own empirical search with no pre-determined answers. It makes a lot of people uncomfortable to go there because it makes you rock the boat of whatever you were holding onto as true and secure.
The thing that doesn't really jive with me is the notion that reason means you are a materialist. That's often not the case. People can make observations about the events, phenomena and experiences of their own lives and draw different conclusions using their various faculties, including spiritual conclusions. At the end of the day our psychoemotional frameworks are all there to help us relate to a complex, incomprehensible and sometimes burdensome reality.
