I wanted to seperate the two subjects to keep you from lulling into a coma by having too long of a thread to read. :^P
"The question, though, is why would human beings choose to hold a philosophical stance that is counter to the theist beliefs of most human beings on the planet, especially when those beliefs are so dismal. Is it possible that a small percentage of humans have a need for random origins in order to experience a kind of freedom that comes from an atheist or agnostic belief system? Any ideas?"
There is a problem with your question, that will make answering it difficult. I can only give you my opinion on atheism, and well, others I have known, but not too many.
Ironically, while atheism may enstill a sort of freedom from certain "laws" of a religion, it certainly does act as a prison as well. You see, its not that atheists don't want a god or don't want to go to heaven and have eternal life. Trust me, eternal life sounds wonderful! However, when I think of the concept, I feel that I would only be kidding myself. So not believing in god sets a couple of restraints on life as an atheist.
1) No afterlife. You know, it is widely mistaken that atheists have no love for life. This is insanity! With nothing more than the life we have now, it is more precious to us, than I think theists can appreciate. No afterlife means that if we make one mistake, our life could be over. Death could come tomorrow, live today. This doesn't mean "Anything Goes", but it is a philosophy of life that really means, don't wait or hold back on experience. Don't hold back on education waiting for tomorrow. Don't hold back, not going to that place in the world. Don't hold back, from moving where you want because of your family or even worse, because you are afraid of change. To do otherwise would be a waste of life, a life that atheists realize is finite, and not everlasting.
2) No set in stone moral structure. Not "no morals" as Christians like to harmp. I've looked all around faiths, from buddhism to taoism to judiaism. With no stone morality structure, one is allowed to adjust. What does Rush say in a song, "Culture is the curse to the thinking class". Culture hurts civilizations. Its good to a point, but it certainly acts as an anchor. Like today, Americans are so full of their culture that they can't possibly understand life in Iraq or Saudi Arabia or Afghanistan. This lack of ability to understand other people is what holds society back as a whole. Atheism allows a bridge to any idea or cultural custom. Take the best, leave the rest.
When I think of god, I think of a book written by men, whether they be Sumerians or Bedouins. When I read most books, I see arbitrariness. When I read the Tao te Ching, I read universality. Wisdom is written in terms that favor no person. So many people believe they follow the right god. So many, that I feel none of them are right.
Why does atheism exist? Well mostly in part to education. Atheism is growing, al beit, slowly. As people are allowed to think for themselves, they grow away from the necessity of god. God is a crutch. It is a necessary crutch, a "necessary evil" as Freud puts it. But not for all people. Atheism exists, because I think it is a logical answer to an illogical question, "Why are we here?" Atheism answers, "Well, we are. Might as well make the best of it. Pass the Cheez-Its." :^)