For me, being religious (or spiritual) has always been a given. When I was younger I couldn't imagine anyone NOT being religious, to me it was just such an obvious thing. Of course there is something greater than us all out there. Of course we should aspire to be better people because that's what's right and God told us so. Do unto others, love your neighbour as yourself. Be a good member of the collective - communities religious and otherwise. As I grew older and met more people who grew up outside of the "Catholic Bubble," I would find that the above was rarely true. You were given funny looks for saying you believed in God, and told only stupid people believed in religion because it was irrational and there was no scientific proof. At first I thought it was just directed towards Catholics (Catholics=conservative=no fun, goody two shoes-es, and are therefore stupid) but now as a (sort-of) follower of a fringe spirituality I see the disdain is equally distributed.
Most of the people I've heard speak about religion think that those who believe is something that cannot be seen or definitively quantified are stupid, irrational, or morons. And these are people who range from my significant other to TV personalities such as Bill Maher. I am always trying to find ways to understand and describe how I, as a fairly logical person, need to believe and participate in something they see as totally irrational. I have several amorphous ideas centering around the human mind's inability to grasp concepts or interact with something that exists beyond our realm of understanding, however nothing concrete.
Thus, I was very pleased to have come across this TED Talk on Facebook today that explains a social scientist's perspective as to why humans have evolved to seek out self-transcendental experiences, such as those associated with religion. It is about 18 minutes long, but it's a good talk and I encourage you all to check it out.