Answer:
Many of us started out as believers. Then for whatever reason we had some questions because the world as traditionally described by Abrahamic religion didn’t seem to correspond to what we were noticing.The question that comes up again and again is this one: you have this god with unlimited powers, who knows everything, and who is all-good, so why is there so much suffering in the world?
Inevitably when you ask a version of this question, your religious elders will give you answers that sound like they’re making up excuses. Or they will shut you down by telling you not to ask such questions.
But the questions don’t go away. You’re left still wondering. Then you learn about evolution and you think: that makes sense! And you learn about religious myths from other cultures and you think: hmm, that’s kind of like what I grew up believing. Then slowly the weird stories from your religion stop making sense.
You cross out the talking snakes and the walking on water and the flying horses, etc.
Okay, you think, now I have a good religion without all the hard-to-believe stuff.
Then you dig deeper and you realize that even the “good” parts have problems: xenophobia, sexism, slavery, exhortations to kill people who offend your faith or to go to war against them.
That makes you uncomfortable.
You decide you need a break from religion to think things through.
You meditate and cogitate and wonder and ponder and you decide that you just can’t adhere to organized religion. You’re going to believe in your god but you can’t in good conscience be part of a religion whose texts advocate actions you consider morally abhorrent.
Then you hear people talk of God. Every time they give arguments for his existence, it sounds hollow. That’s a really weak argument, you think to yourself. Over time you start rolling your eyes when people tell you that everything happens for a reason or that God will take care of it you or that someone who has just died is in a better place now.
Slowly, you start to realize that you just don’t think there is a god. This frightens you at first because you’ve been raised to think that atheists are immoral. But when you try to believe you just can’t shake the feeling that you have no more evidence for the god you believe in than the ancient Egyptians and Greeks did about their many gods. You come to view gods as nothing more than the expression and translation of our hopes into mythological form and the ever-shrinking total sum of what we do not yet understand.
That’s why many of us don’t believe. We’ve read the books and heard the sermons and attended the religious services and participated in the rituals and sung the songs. But we also studied the history and exposed our minds to more than just the internal logic of the religion we happen to be born into. And once you’ve opened those doors, it’s almost impossible to close them again.