Marx was dead on when he called religion the "opiate of the masses". Modern human society is hooked on religion harder than any junkie on smack, crack, or pot.
Lets use Christianity as an example. Christianity grew out of Judaism, which grew out of various local cults throughout the Middle-East. Like any other religion, it's mythology strove to explain occurances that weren't easy to decipher with their current methods. As happens with any good religion, a system of morals and strictures grew out of the faith.
This was all well-and good, while people still enjoyed being wrapped in the blanket of mythology. As science slowly appeared, and began answering many of man's more perplexing questions, mankind searched futily for a way to maintain religion in society. The came up with the cracked idea that society couldn't survive without religion, because "where else could we get our morals?"
So now that we have rendered the mythos obselete, people still cling to the ethos of religion in a lame attempt to maintain their beliefs. Society is in denial about it's problem. When will we see Faithful Anonymous?
Addendum: The above really only applies to theosophical belief systems, which is what I normally classify as religions. I don't consider Buddhism, Confucianism, and their ilk religons. I'm actually a strong supporter of Buddhism.