God, in His infinite wisdom, created atheists so that believers would have someone else to argue with so as to prevent them from wiping each other off the face of the Earth and created believers to keep atheists to preoccupied to engage in their second most favourite activity . . . eating babys!
Genesis 1:31 And God saw every thing that he had made, and, behold, it was very good. And the evening and the morning were the sixth day.
Genesis 1:32 Then on the seventh day, having rested, God saith onto Himself, "This is boring." so then, atheists and believers, created He them.