Personally, I became an atheist more because I'm "not seeing it, not feeling it".
I don't see a deity in my everyday life. Neither supernaturally or 'naturally'. I can see how others would, however. My feeling is that believers have a combination of a 'hunch'; a 'gut feeling' caused by looking at the complexity of life and matter, combined with a variant on Pascal's wager buried way back in their subconscious. This awe, this gut feeling, plus an underlying, possibly subconscious, thought of "well, at least I'm trying to please God, so if I'm wrong in the details, that's what matters." is what I think sums up faith in most people. That it's a choice, often contrary to experience, with a small amount of Pascal's wager thrown in. I know it's dangerous to try and explain what faith is because for believers it's something mysterious and supernatural, but this is my personal understanding based in my current perspective on life.
When I say "became an atheist", it's not a new religion I've embraced; it's more like a 'waiting room'; waiting for God to show up. The default position. Not that I sit and wait actively, but I sit in this 'waiting room' for God just as I sit in the 'waiting room' for Sasquatch, alien visitors, unicorns etc. I wouldn't mind the existence of any of them. I wouldn't mind the existence of a God at all. It would depend a little on how this God was personality wise, but my belief would not be dependent on this deity's personality or reasons. I have a line of work that unfortunately makes me somewhat desensitized to other people's (strangers') pain and suffering. I have to be, otherwise I couldn't function in that job. So perhaps I have a little different perspective on a potential God and those areas of life. Or rather, although I agree that there is too much suffering in the world, I'm not focusing on it much in my atheism. If God exists and he's an a**hole, he'd still exist. He'd just be a lousy God (yes, I write 'he', but only to avoid having to write he/she/it/them all the time...). So suffering is not such a good argument for God's non-existence (only certain specific images of God in that case) in my opinion. I'm not an atheist because "I'm angry at God". How insane would that be? I can however be angry at the God other people think exists, or rather that concept. There's a difference.
Now, when I said I'm sitting in the waiting room awaiting further evidence, many believers will knee jerk: "But you have evidence all around you!". This is part of the 'hunch' and 'gut feeling' I was talking about that people have. I have to admit that as I have dug into scientific theories, I've found many amazing things in nature - but they have a natural explanation and origin. From the formation of the universe and the matter within, to the emerging species. There are gaps in knowledge here and there in which we can put a creating deity, like the start of life or the start of the universe and many others, but seeing how the 'God of the gaps' (the deity put into any fitting gap of knowledge) has had to 'flee' the area every time new knowledge has filled that gap, I don't see it as a smart thing to put God into them in the first place. Now - even the natural explanation of the origin of the universe and species etc. does not preclude a deity. So this is not necessarily a good argument for God's nonexistence either.
Saying it is could be said to be like mechanically analyzing the way a paint brush has stroked a canvas in certain ways, naturally creating certain shapes because the brush was moved that way, and that other shapes would have been created had it been moved differently - without saying anything about the artist, because we know nothing about the artist and therefore couldn't comment on him 'scientifically'. However, there is a difference, which I'm not going to go into detail about here, but there is a difference between the two scenarios; a creator is not needed for organic molecules to bond, or for matter to arrange itself in certain forms caused by gravity. Then again, the God of the gaps can be inserted here, because why does the universe have these properties? While there are several logical answers to that, it's not a stupid question to ask. But of course; artists can be found and interviewed any time one would want, and even if one particular artist was nowhere to be found, others could be found, interviewed, studied while they worked etc. and in extension, a good idea about the artist in question could be formed as well. God however is strangely absent or silent.
Well, for most of us anyway:
Some people have very vivid, physical or at least psychological encounters with God. One is not supposed to question this, because it is deemed to be inappropriate and rude to do so. On one hand, I can agree; such an experience can't really be discounted by me simply because I haven't had them myself. But several questions do arise. Why do people of different cultures and religions meet different Gods? Why does God show himself (he, she, it, them...) only to a few elect people? Why does he help these few people and not others? Etc. One obvious answer would be that there are many different existing Gods, another answer that only some of these are real experiences (who's to judge? "that's not my God, so can't be real" ?). Another answer is that none of them are real.
I think that if science hadn't answered any questions regarding how the universe and species (and possibly life itself) emerged, I would have been a deist based on the above and other questions, and lack of personal experience with a deity. As it is, I don't think I would have been a theist.
-But it seems I can go on and on here and cover many different topics; I can already feel my post being quoted and dissected a sentence at a time, and the resulting conversation carried in many different directions. But I was trying to make one, more or less coherent point: I don't share the 'hunch', the 'feeling' that believers do. Or maybe I do to some extent, but in a different way. I too can feel awe at complexity and beauty, but I guess like a teenager at a sci-fi movie loudly commenting on how all the special effects were made, instead of really getting sucked into the wondrous fantasy of the story, I look at nature and see those underlying principles that made it come about, complexity from humble beginnings, not complexity from complexity.
I haven't had any great revelations or experiences. Or maybe I have, at least on the same level as many believers, but have interpreted them differently.
So I'm sitting in the waiting room. This does not make me an agnostic, because based on currently available (available to me) evidence and experience, I don't see God. So it makes me an atheist. Does that mean I think God cannot exist? That I refuse to believe no matter what? No, I hold that open of course. But I'm not going to be a believer in an attempt at scoring in a possible game of Pascal's Wager. It shouldn't be hard for a God to show himself. If I'm not worthy of a visitation because of something my ancestors did, however unfair that would be, at least I could be sent a messenger? Some would say I am a God myself, but in that case it won't really matter what I believe in this life; I should be able to take care of myself in the afterlife then, and believe it or not, I won't judge myself harshly.
That does not mean that I think all believers are deluded (or rather 'insane'). I happen to think some of them hold obvious false beliefs, but so do believers about other believers. I happen to believe that some believers have a wrong understanding of reality because they discount what scientific discoveries have been made (or they have been told some skewed version of that scientific discovery) in favor of a literal reading of a book written thousands of years ago. But aside from that, I feel I respect believers for their beliefs. But there are questions that arise as a consequence of believing, and the answers don't satisfy me personally. This is probably why I post "atheistic thoughts"; to try and get answers, or get people to really think about their beliefs. This is probably why theists post as well.
