It's a great question. And Scripture tells us God HAS, in times past, far more obviously and miraculously revealed Himself, to large numbers of people (as per the miracles of Noah and Jesus) and to many individually). And if you ask most Christians on this forum, they will tell you that God quite clearly has revealed Himself to us. But our experiences are all different, as God knows exactly what each person needs for faith - and these are unique to an individual. Also, God is not just after mere belief in His existence - clearly pharaoh and all those seeing Jesus raise Lazarus knew His power was of God - but many others seeing such things would not believe and obey. As God led Israel in the desert via physical manifestations, many still did not truly take him into their hearts, as they had the kind of belief Scripture says the demons have - mere intellectual belief.Ken: What’s the worse that could happen if God were to address the entire world at once; in an audible voice from the clouds, in a language each of us could understand; to clear up all the misunderstandings everyone has of him?
Another issue is, WE don't get to choose how GOD chooses to reveal Himself to us. And His purposes and methods are perfectly known only to Him. And obviously, there are many God chooses not to reveal Himself to because He knows they don't really want to know or follow Him - as well as that no miraculous thing would ever change their heart and attitude. People saw Jesus do all manner of miracles, and yet they accused Him of doing these by the power of the Devil (which is "Blasphemy of the Holy Spirit." So, for such people not truly desiring to know the truth about God - really, knowledge of God is useless to them - and so He withholds such knowledge as they don't truly desire it - as most such people know that "if" God exists, they to follow Him faithfully, they would have to "get off the throne!" That is, instead of deciding for themselves what is right and wrong and doing as they please, that they would and could no longer be the "little god" of their life - but they instead desire to stay on the throne of their life - the one that is rightfully God's! And so, for such people unwilling to obey God - even if they discover His existence - He'll not make things anymore obvious for them. He doesn't do magic tricks for those determined not to believe!