"I don't understand why almost all the threads that run the longest on this site have to do with atheism/theism debates"
In our pointless world we all generate meaning from our worldview. Joy, anger, fear, all are channeled and focused by what we believe and our responses informed and mediated by it. For some it is family, others it is work but for most it is religion and god(s) - it(they) provide purpose when none exists, they cause society to build pyramids and to hand over scarce resources to men in dresses and give in return peace, hope and devotion. These discussions are so important because they are so fundamental to who we are, what we do and why we do those things in our brief, flickering existence.
I understand the love of faith based magic thinking. It is an exhilarating drug with easy highs and sumptuous lows. It is glorious, however, like all ideologies (Nazism and Stalinism are two easy examples) the cost to the individual can far exceed the collective benefit. For those of us who are outside religion it is easier to see the long term cost of a faith worldview (ultimately by providing false but comforting answers it stifles our ability to look for or generate novel meaning that may better meet our needs - a bronze age, mystic cult is not suited to a technological and scientific community.)
This debate and the millions that will follow are our collective way of un-ravelling and discarding millenia of magic based culture and replacing it with fact based humanism.