Personally, I was lucky enough to be born in the United States in the late 20th century (as opposed to 500 years ago).
I think this is on topic...
The differences between the two "methods" and their practice between the secular, scientific community and the religious community was made VERY clear to me at a young age (though, granted, my postage stamp-sized little world cannot be said with certainty to be a true representation of the entire nation or world). I was very into Cosmology and Astronomy and Biology at a very young age. Begged my parents for my first telescope at age 8 or so. I recall visiting a planetarium at a university and getting access to one of the professors on staff. I asked him about 100 questions, rapid fire, in a span of about 30 minutes. He was very patient with me and took no offense whatsoever to me saying things like, "That doesn't make any sense to me." He was kind and seemed to relish the opportunity to discuss the material with a curious, young "skeptic" who did not simply take things as true based on his authority. I was 12 years old.
A short time later, my parents enrolled me in Catechism class (Lutheran, Missouri Synod). I was actually kind of excited about it. I had so many questions about the Bible and about lessons I had been "dictated" in church and Sunday school, without any prior chances for questions or any interaction whatsoever. Instead, I was greeted with anger and ostracized by our head Pastor, whenever I *dared* to ask simple, honest questions, like:
"How could Noah POSSIBLY have fit 2 of every animal on the boat?"
"Why don't babies go to hell?"
"If Jesus could feed those people using miracles, why didn't he feed ALL the starving people of the world?"
These are simple questions one should expect a child to ask. One should have answers prepared for these questions. Instead, I was made to feel like even asking these questions was evil in and of itself. I was rebuffed and chastised for my curiosity and critical thought.
It occurred to me, even at that young age, that, possibly or even likely, the pastor threw his little fits because he didn't have a leg to stand on. While this did not make me doubt theism, it did make me step back and doubt the dogma not just in Christianity, but in all the religions. Such critical thought and skepticism has served me well to this day. So, I suppose the Good Pastor deserves a "thank you". What made me discard theism was ongoing education in the physical sciences. At first, I assumed we were just studying "God's creation". I slowly came to realize there was no need of the God hypothesis to explain anything we know or observe. We either know, or we admit we don't know and look for the answers using completely secular methods.
So, here I am today, an agnostic atheist. Sure, there might be gods. I could never say with 100% certainty that there are not. But I live each day without any need for that idea.
To circle back to the topic, I think a LOT of today's Christians are, for all practical purposes, secular in much the same way. They aren't using the idea of theism or the Christian dogma to make any important decisions in their lives on a daily basis.