This simple chart provides a fairly accurate description of why prayer serves no real purpose. Assuming that the god at which religious believers are directing their prayers has some sort of plan for them, as most Christians insist, prayer is either redundant or futile. If one's prayer happens to coincide with the will one one's preferred god, it ends up being redundant. On the other hand, if one's prayer conflicts with the will of one's preferred god, it ends up being futile. In either case, prayer serves no purpose.
I should note one important omission from the chart. Prayer, even if it has no purpose in the sense described by the chart might temporarily make a believer feel better. For this reason, one could argue that temporary self-soothing is the only purpose that could be served by prayer.
