Oz, I think that casually accepting cultural environments doesn't discriminate between philosophies and thus yes, there are plenty of people who are indifferent to the whole issue who may think themselves atheists without ever having meditated on the subject at all.
However, for lay people on both sides as it were, you can say it comes down to choosing an approach you respect more. I don't know all there is to know about science, but I know the scientific method is worth respecting,the basic humility of seeking to prove a theory wrong, that to be a skeptic is preferable to believing or subscribing to any system / belief. Challenging questions is what improves us, and any limits on that, any absolute presuppositions that suggest we have to assume a Creator before questions is flawed. That if there is a God above all everything we know, a primestarter, it wouldn't align itself with such limited dogma and scripture at arbitrary points in the human line. Furthermore a God displaying human traits is not worthy of being held in such esteem above other humans. We have enough examples of good people on earth to take heed of who aren't coloured by a such a negative score in the bad column. Our values evolve, the world we live in evolves and our attitudes develop as we go. That God put no mechanism in the Bible for allowing for this was frankly rather short sighted if you ask me, and if there is a passage which allows for it, it clearly wasn't emphasised enough.
No, I don't know all the parts of the bible, nor all the scientific answers and I ought to rectify the holes in my scientific knowledge where I can, which is why I say atheist agnostic, I cannot say with absolute certainty that there isn't something out there, but to limit oneself, especially to a philosophy that is SO divisive is just bizarre. I don't mean to offend you personally in any of this, and I apologise if I do, but there are just innate issues with any organised structural system that will always reveal their limitations.
There's plenty of useful tales ( and plenty of repugnant stuff too ) to be taken from the bible and other morality handbooks, some of them still relevant and admirable but I think religion will continue to face opprobium and dissent from us lot so long as it insists on limits, and on rigid values that many contemporaries find irrelevant, antagonistic and just plain wrong.