I just assume it's a balance. The nature of the physical universe seems to boil down to matter and anti-matter, electrons and protons, etc. Good and evil is an exceptionally complex emergent behavior from layers and layers of progressively simpler systems. Our world happens to be made up of matter, and it's a bias that allows for our existence. Whether or not you consider that clever, it's a bias of fundamental necessity; by definition, if you put matter and anti-matter together you get a release of energy and then nothing. It's a local bias, though, and presumably there's some antimatter somewhere to cancel our existence out.

Good only has meaning in relation to evil. If evil didn't exist, then good wouldn't exist either. Free will only has meaning in the presence of choice. If there wasn't a choice, then we wouldn't have free will. It seems like in order for human spirit to exist and have spiritual importance, there has to be evil. We can create local biases of good and enjoy it, but to eliminate evil completely is to eliminate the meaning of life.