Because they all think that their God is the right God. Remember when you were younger it was always "My dad's stronger than your dad" or "my bikes faster than your bike." Well adults never grow up and get over things. "My Gods better than your God," historically instead of it just being a kid thing they kill over it, always did and always will. How can anyone find out which is the right God (when there's only one anyway) when they're still fighting over who invented the first television first.
