All newborn babies are atheists. That is they have no concept or any kind of belief in any kind of god or even a platypus. They must be taught about gods to ever have an opinion. They can later have an opinion that God is real, or God is imaginary, or not sure about the reality of God (Agnostic.)
Most babies are fed meme viruses about the God their parents believe in. American and European babies are mainly led to some kind of belief in the family's God by repeated meme input on a daily basis. Arab and Turkic babies are fed memes about Allah. Jews are fed memes about JHWY.
However, God is invisible. God makes no noises so we cannot hear him. God is intangible so we cannot feel him. There is no phenomenon that we can observe being caused by a hypothetical god.
This is an obvious set-up for a kid to question this belief in gods. Why do we believe in something we cannot see, hear, feel, or observe phenomena caused by the thing that is invisibl?
A minority of children do not believe in gods. I am one of them now grown up and still a non-believer.
A majority of people and children are agnostics to some extent on a wide spectrum. At the left end of the spectrum, perhaps 1 or 2% of devout Theists occasionally harbour transient doubts about God.
Some in the middle of the spectrum believe in God but frequently have questions about their belief, and the existence of their particular god or any god. They work constantly at suppressing their doubt.
Then on the far right of the spectrum are people who are weak believers, largely because of the deluded hope of immortality. Yet they feel definitely that Christian or Islamic dogma simply does not make sense. Even God does not make sense. However, this person takes Pascal's Wager in the hope of immortality and or fear of Hell.
Some Atheists may even be Agnostics. They reason that there is no evidence of God, but there is some remote possibility that they could be missing something. They think about a possible God, but soon give up and admit non-belief.
Perhaps the Thread author is right; almost everyone is to some extent, an agnostic. Agnosticism varies from 0.1% to 99.9%.
Amergin