I wonder if this is the best place to put it, but one of the better books I read on religion (named literally: Religion explained) did a multi-factor approach to religion and is one of the better books I've read on this subject.

Some of the reasons:

1) We're hard wired to remember and transmit some types of information - Want to remember the X different types of blood vessels? Hard problem. Want to remember a story about a mountain that eats people? Much Easier

2) Religion and religious structures provide order

3) Religious systems explain and help handle death

4) They provide a form of control against randomness (pray and your child will not die.)

5) Religious systems as social moderators and interaction protocols

6) Act as the super set for superstition and offer explanations and systems to handle unexplained events.

I may have missed or mixed a few points, (Its been a while.)

ALL these reasons combined, ensure that religion will be always be created, and it fills, or ends up filling, multiple key niches human beings encounter

And finally because of our internal wiring, we will always end up remembering and building on these traditions.

So as you say, religion for many reasons really is an emergent property of human existence.