Personal experience is unreliable but interpretation of that experience is, in my opinion, probably a mixture of experience, observation and a person's natural predisposition towards belief or non belief.

For example, personal experience alone didn't make me an atheist. I was raised Christian and had a positive experience on the whole, of being Christian. There was no real personally benefiting reason for me to become an atheist on grounds of personal experience alone because my personal experience of religion was actually overall quite positive and fun, as well as being something I was very emotionally and socially attached to. I actually miss it sometimes, in the way you miss the childhood magic of believing in Santa.

What made me an atheist was a question of whether there was any evidence in the wider world that the God hypothesis was correct and plausible. I gradually found that I couldn't produce any evidence of this, either from personal experience or from looking at the wider world around me and the observations of others. Additionally there were other explanations which, to me, were far more plausible. After that basic rejection of the concept of God, I started to notice the morally flawed, destructive and inconsistent aspects of the bible, but it wasn't my personal experience of religion that lead me down that path in the first place.

I honestly think that some people are just hard wired to believe and some people are hard wired to question. I think experience and environment play a role in this process but I think that, for a lot of people, doubting and questioning is a personality trait that surfaces naturally.

It's almost a nature vs nurture issue. Skepticism (and atheism) springs up among people of all cultures, as does a belief in the supernatural, no matter the background and the dominant supernatural belief system. Sometimes belief or non belief is entirely cultural or based on experience growing up within a particular faith but often it's something that we gravitate towards spontaneously and naturally.

I honestly think that, in many cases, the inate need to either accept and believe or to keep questioning comes from your natural predisposition.

Having said that, all of the above is based on my personal experience, so feel free to take it with a pinch of salt...