Your presumption seems to be that people are religious first before becoming agnostic or atheist.
I went to Sunday school from the age of 5 to 14 but I was never religious .I t was just something I had to do and I disliked it intensely. it spoiled most Sundays.
My sons were brought up without any religious influence at all. It was something that other people did. They and most of their friends are mostly the same. It is just something that other people do and is of no interest to them.

Numbers 3, 8, 14, 15, 19, 24, 25 resonate with me.

And I would add that I noticed a strong tendency for Christians to enjoy punnishing others, even though that is not at all what Jesus is claimed to have preached (though it is in line with the God in the Old Testament, which Christians say no longer has relevance since the advent of Jesus).

I have a religious friend that has been kicked out of 2 churches and still believes in the bs. I won't air his dirty laundry here, but it's 2 faced religion at it's finest.

Amazing, just amazing what church people getaway with.

It started when I began to realize that the concept of prayer was so ridiculous and made absolutely no sense or logic.I questioned the belief that god gave humans free will and that this was the reason they are capable of evil actions etc.Common sense told me at a young age that a god would not give free will to humans due to being aware of the consequences.

When I found out the Easter bunny was hiding chicken eggs.

Nope, none of them covered my 'epiphany.'

Fortunately, neither of my parents showed any interest in religion. On Sunday when most people were at church I was either in a local park or sitting on the bank of a river with my fishing rod.

For me it was figuring out Santa Claus and the tooth fairy didn't exist, and I decided it was a similar type of lie.

I’m quite sure these are all SIMILAR to the reasons many on here experienced, myself included.