kappa: yes, imagine a world with no religion... its easy if you try... Most people are inherently predisposed towards being religious - if by religion we understand a more general notion of "irrational belief", not just adherence to a traditional church.
There are plenty of reasonable speculations how and why such tendency would develop through evolution as a survival trait.
Most people who are claiming to be non-religious or outright atelists hold one or more irrational beliefs - often militantly so. They take on trust what seems absourd to many, they refuse to read the opponent's arguments, sticking only to their own literature, sometimes they even refer to some forces and principles of nature that have no natural basis.
People believe in state being all-knowing and all-powerfull - which was an aburd notion 150 years ago. People believe in environmentalism, socialism, all kinds of other utopias and distopias. People believe in inherent superiority of one ethnicity over another one.
Those are all religions. The conventional religions have at least an advantage of passing through growing pains and settling in a non-radical, conducive to civilisation patterns.
It's easy to explain - thoug I will not do it here - that most newly- appearing quasi-religions filling the gap will be of much more disruptive nature.
In short, conventional religion(s) is an adaptive survival feature developed by humanity.
miko