In my case, it was a lack of evidence, and the cult-like veneration, er, “respect” accorded to the clerisy of the branch of Christianity that I was raised in.
I am not a Christian because my parents raised me Christian. They didn’t. And my three daughters were all raised Assembly of God and were even members of the Junior Bible Quiz Team. They knew their bible and were very involved in the church. That didn’t save them. Only the blood of Jesus can save them.
Their mother divorced me (no fault. She was just tired of being married) in the late 90’s when my oldest was 16. Now one is a Bhudist and the other two are agnostic. So far...
Does it bother me? Yes and no. I love them and would like to see them in heaven, but Jesus is very clear on the matter when he describes who his “mother and brothers” are.
To the “perfect” Christian, blood is NOT thicker than water. I’m not “perfect”, but I am being perfected.
There are plenty of people I can share the gospel with beyond just my blood relatives. All of them are equal in God’s eyes.
I said, “I am not a Christian because my parents raised me Christian.”
I needed to follow up with, “I am a Christian because the Lord called me via the teaching of others.”
I left the impression that I am not a Christian. Sorry.