My intent is to help those that ask the question in the title to think. There are those that will believe God does not exist. There are those that acknowledge God, but wonder why He is not walking amongst us right now. Is the response that follows the definitive answer to this question? I doubt it, but it is worth, at least, trying to answer.
What needs to made perfectly understood is that this is about free-will, the ability for each person to make choices. To make these choices though there needs to be an understanding of the facts in these selections. Some would be called common sense while others are reached through research and study, but they are still an act of free-will.
All of humankind are flawed. We all make decisions that hurt ourselves and/or others. It is due to this flaw that there is war, prejudice, neglect and the list goes on and on.
Does this flaw mean there is no God? No.
Free-will is this flaw, but it is a duel-edged blade.
When those with the ability to influence the masses understand that God does exist then things like laws come into being. These laws usually help people to make the right choices. On the opposite side of the coin, when God is removed from these laws horrors can take place. A prime example of this was Adolf Hitler and his inner circle. They did not believe in God, but believed man was the ultimate power on earth. As a result, laws were made that did not include God and as a result nearly 13 million people died horrible and unnecessary deaths.
When humans decide they are god, other humans die as seen not only in World War II Germany, but in ancient Rome as well. Two prime examples are Caligula and Nero. Both thought themselves to be gods. The former killed his mother, wife and slept with a horse as well as killing thousands of Christians for sport in the Coliseum. The latter burned Rome so he could make a new city named after himself, thus killing thousand more when he blamed it upon Christians.
So the very fact that humankind is here today shows there is a God, but why is he not here?
He is not here in person, because if you can believe in something that seems intangible then your belief is stronger than it is in something you can see and touch. If you can see something you can become oblivious to its meanings and purpose.
God is not here in person to allow those that wish to listen to their flawed mind and body to do so. For God is seeking the seeds from the chaff. Therefore, when the seeds are planted, within their faith, they will germinate causing new growth, as they are bathed in the light of God through knowledge and understanding. While the chaff, those that refuse to acknowledge His existence will become what they become. Some to the point of become like those before that placed themselves above God, just because they could not see God.
Humankind causes bad to happen in the world. All because humans have free-will, that is why it was called the forbidden fruit. For from this fruit from the tree of the knowledge of good and evil God knew that only death and destruction would follow, which it has.
dreamwalker1960 
What makes you think that the people who are asking that question aren’t asking it because they are thinking?
Hitler was Roman Catholic, but, even if he wasn’t, his actions were a result of his anti-semitism and not as a result of his religious beliefs. And if non-belief leads to immorality, how do you explain atheists who do good and theists who do bad? You don’t need god to be good.
Hitler may have started as a Roman Catholic but it is documented that he switched to the occult after WWI. As I stated if you read fully it is free-will that causes humans to choose, but most laws that are inherently good have their roots in Jewish and thus Christian believes.
It is free-will that is the determining factor. In each there is an inner conflict to either do evil or do good. I am not saying there can not be atheists that are good, but if they really researched where their desire to do good comes from they may just get a surprise.
I am saying in the past when those that ran governments placed themselves above all but themselves, which included a “god” then they committed truly evil acts. As the saying goes “ultimate power corrupts ultimately.”
Hitler did not worship the occult. Throughout his political career he made numerous referenced to his belief in the Christian god. What do you mean by “inherently good”? What we consider good is subjective. Even Christians disagree with each other about what constitutes good. Much of what we consider good today comes from the Bible, but much of what we see as good contradicts the bible. And much of what is in the bible (as far as morality is concerned) comes from earlier cultures.
If it was subjective then by your description Hitler was a good guy and did wonderful things for the world. During his rule laws that you could call “subjective” first led to not allow those that were not mentally suitable to not have children. It was ultimately through “subjective” laws that led to the arrest and then death of Jews, freemasons, homosexuals, gypsies and others.
It is these “subjective” laws that will lead to death and destruction as has been proven throughout history, because “subjective” laws place humans in power higher then others. As a result you end up with people allowing things like veterans of war to die from lack of care, to people wishing to silence those that do not support their views like Ms. Leriner of the IRS has done and feels they have committed no wrong when they have. All because they are being “subjective” about the laws. I prefer to try and keep the “inherently good” laws.
Hitler certainly thought what he was doing is right. If Hitler had won the war, maybe we would agree. Hitler did terrible things, but my viewing them as terrible doesn’t mean that everybody agrees with me.