Why Atheism?

I'm an Atheist and people around me can't seem to grasp the reason behind it! Being an atheist does not mean I don't believe in an higher order. It simply means I refuse to define that Higher Order in mere terms of stone statues. I believe in something much more practical, sophisticated but delicate and yet at times vicious. My faith is reserved for someone or something called Nature that made my existence possible. I chose to believe in nature rather than a God maybe because it is much more logical or maybe because I'm terrified of someone out there who can control my calling or future or destiny or fate.

How hard is this reason to not understand or accept?

If you are an atheist, I would love to know your reason for choosing Agnosticism..

What is our Purpose?

The question "How are we any different from an ape or even an amoeba when all we seem to properly can do is reproduce just like them?" The only difference we successfully have established thus far after 85 million years of evolution is E=MC square and that we don't fling poop to eliminate competition while impressing the alpha! Something I'm sure our evolutionary predecessors couldn't understand. Then again, Is It that Big of An Evolutionary Feat? The purpose of this post is that I've failed to find a purpose. A purpose for our superiority and our genius, a purpose for our existence, a purpose other than surviving, a purpose for 8 Billion of us! It was terrifying when it finally dawned that I was not only different from every other human being but also I was no different from all those plants and animals. Oh, well! I am a little different because all those animals and plants "without conscience and inferior to us" lived Symbiotically when all I am is Parasitic.. 

Would that mean our purpose is no different that of a leech's?