I don't agree that atheists reject these traditions, their rejection is superficial, they merely reject the explicit belief in a deity, but keep most of other traditional beliefs intact, it is the same with habits, they reject the explicit material habits of religious practice, but keep the ideal habits of values and thought patterns. Only when this rejection becomes deeper can reason (where knowledge replaces faith, not becomes another object for faith) begin to form its own habits and practices. To keep the world in darkness just to make people eat healthy seems absurd.
You are correct when you say that atheists often reject the idea of a deity but keep many of their prior traditions, habits and values intact. This is mostly a matter of self preservation for the farther one travels from those traditions the greater the potential for self harm.
There is nothing wrong with searching for a deeper truth but to characterize knowledge as a replacement for faith is error. At its most pure and fundamental level knowledge is faith and faith is knowledge.
You have rejected faith and are walking in search of 'light' to dispel darkness from the world. Are you certain you have not made a wrong turn and are instead walking deeper into shadow?
Imagine for a moment that this is not an abstract philosophical question but a walk down a twisting and branching alleyway. First there is a single way with no choice but soon we come across a fork and from the single path we find two. To the right there is carefully laid cobblestone engraved with the words of theism. To the left there is newly pressed brick and a crisp printed sign labeled atheism.
As we walk down these paths we find the walls of our alleyway glowing with living and undulating writings. These are runic words and assumptions indeed the core of each choice. As we accept them they detach themselves from alley walls gently merging with and setting over us forming a fine film over our skin, eyes and ears. Their function is that of a filter interpreting and cataloging the world around us.
If we choose the brick road we soon come across a second fork. Here we see a dark and shadowy opening into nihilism and a large and particularly well worn path into hedonism. Small branches into esoteric philosophies can also be found. The road of hedonism leads to a smaller opening into ethical hedonism and finally a tiny path into utilitarianism. Here the road ends and we find ourselves facing a brick wall covered with the words and beliefs of the choice we have made. This is were my own journey took me the blind alley where I spent 15 years thinking I had arrived at end of the road.
Does rejecting atheism on purely utilitarian grounds bother me? On the contrary it is the purest, cleanest, and most liberating rejection of atheism, ethical hedonism and utilitarianism that I can possibly imagine. It is the final realization that the complex writings on the brick wall translate into a single sentence. "Wrong way turn around!"
The arguments in this thread should not be thought of as strong theist arguments. Indeed a true and strong believer will likely find them all a little off and a little odd like a TV whose tuning is sort of correct but just a bit wrong throwing static into the picture. They would correctly argue that it is through faith not through happiness that creates a true belief in God.
The words of faith, however, cannot reach those far along the brick road. They are blocked or interpreted as nonsensical by the filter of assumptions those on this road have adopted. To grasp these deeper arguments one must first turn around travel back to the original fork in the road. Only then as the assumptions of atheism peel away is possible to hear and truly consider the deeper arguments of faith.
The arguments herein will not prove convincing to all atheist as the filter each atheist had adopted is different. My sense of self preservation kept me far away from the shadowy road of nihilism but there are branches there that teach that life has no intrinsic meaning or value. That life is insignificant without purpose and that even continued existence is meaningless. For those that have fully accepted this belief it is possible that even utilitarian arguments of health and happiness will be filtered out as nonsensical.
My argument is that atheism is false. As for what is true I cannot help you for I have only taken a few steps down the cobblestone road and do not yet know where it will take me.