"Religion is the opiate of the masses." Karl Marx
I stand by that quote. A Commie though he was Old Karl had something there. Without religion SOME people would just be completely insane. As a child you question death and if you are in a devoutly religious family then they have an answer for you. As a child you question why rules, They have an answer for that too. Religion offers everyone what they want most the answers to the unanswerable. there are those of use who could handle life without belief and those of us that couldn't. I believe in a god but I would be fine with life if I did not believe. The vast majority wouldn't be fine. It would be a chaotic and unhappy world if nobody believed in anything even if they are just pretending to believe religion is the only thing keeping some really unstable people in check.
On the other hand you can use religion as a tool to control these unstable people hence radicals of any religion and it seems to be gravitating towards making this world chaotic and unhappy anyway.