>>2810062>>2810064The main purpose of religion from a utilitarian point of view is to provide a set of coherent moral values for society. It's not enough to have a set of rules though; those rules need to come from a divine authority. People must truly believe in the righteousness of the moral values that they adhere to, and they must believe that even when no one else is looking, God is still there watching.
The problem with atheism on a societal level is that not only is it impossible to convince every other atheist that your set of rules is the correct one, but to make every other atheist believe truly in their heart, which is a prerequisite for a healthy, functioning, high-trust society.
Now if you want to get into the spirituality of it all, Christianity isn't necessarily the only true religion, but it is the most true religion. A culmination and progression of truths that came before it. God is a force, and religious dogma is the method by which God communicates what He wants to us.
