You do not care why God allows suffering since it is quite apparent you do not believe He exists. Funny thing about that, in Iwo Jima they did not think the bomb existed, until it hit them. So you see, it really does not matter if you "believe" there is a God who is in control of everything, your belief, or non belief will not effect Him, but had the people of Japan known that USA would have dropped that bomb on them, I think they would not have bombed Pearl Harbor. Perhaps you should rethink your blasphemous attitude?It's true that suffering doesn't negate the existence of god. "He" could exist and allow things like slavery to go on for centuries. It would just mean he is the biggest douche bag of all time.
God allows suffering because without suffering there is no such thing as joy, peace, etc. etc.Clearly there can be peace without suffering. Peanut Butter exists independently of Jelly, even though it makes the other taste better.