Theory: Religious beliefs are rationalizations designed to reconcile our concrete observations with concepts or beliefs instilled in us by social conditioning. As more people have an increased awareness of the physicality of the universe, doubts are cast on old belief systems and these rationalizations become more elaborate and abstract.
I think the desire to form these rationalizations is so strong because these various concepts and beliefs have ramifications beyond the physicality of science. They play a large role in how our culture has evolved, how things like entertainment media, economics and legal systems are structured. This is probably too far-reaching of a theory to be easily proven or disproven, but to me it answers some questions, perhaps.