I dont think that you can seperate religion from spirituality or vice versa, they are in the "essence" the same, both revolve around the concept of an undefiened super power, some choose to call it god, others the universe (read the secret), karma, mother nature, and some see it in a cow!
None the less we are all guided by this "power" I think that is because we need to believe in something, it sort of justifies our existance and doings, our relationships, our fortunes, our choices, we as humens need bounderies to exist it makes us feel safe and grounded, it gives us an excuse to ignore what we dont know to cover it up "the unknown" (as its scary to think about it), it sort of answers the unanswered question without really answering them,,
Bottom line i think we NEED to believe in "it", whatever it is,, or we will go crazy...