Atheists are not devoid of morality as some theists think.
A theist has a religion for spiritual reasons and from what I perceive, also largely for the hope that there is something after death; they also may possibly wish to think that life is to wonderful and detailed to have 'just' happened and thus credit a god for creation of the world they see around them -as many people have before them. While it is a nice notion there is no sound evidence for such a fanciful hope, although (for the Theists dreamy minds-it can not be disproven...yet (lol)) Perhaps death and creation does happen in such a way (though then one could argue any number of stories for creationism).
What one may find reading more into the histories of religion is that, modern religions should not be taken blatantly at face-value. Religions and worships have their beginnings and finding their roots can tell you more than just the spirituality lessons that people garner from them, but about past cultures, archaeology, geographic distributions etc.
Check out this link
http://www.youtube.com/watch?v=MlnnWbkMlbg
(Also the above dude's link has other episodes that span into philosophic ideas and get away from the religion aspect).