Gen 4: 5 But he did not look with favour on Cain and his offering, and Cain was very angry and downcast. 6 Yahweh asked Cain, ‘Why are you angry and downcast? 7 If you are doing right, surely you ought to hold your head high! But if you are not doing right, Sin is crouching at the door hungry to get you. You can still master him.’ 8 Cain said to his brother Abel, ‘Let us go out’; and while they were in the open country, Cain set on his brother Abel and killed him.
I find these verses get to the heart of the matter for me.
God, who in eternity knows how it will turn out, comes down into time to warn Cain that sin is growing within and will get the better of him. He knows what will happen because He has every moment before Him. He is aware within eternity of Cain’s decision in time. Additionally, God’s infinite knowledge includes, knowing the person fully, and therefore what the person would choose under certain circumstances. These verses suggest to me that our will is completely free; Cain actually had a choice, he could have chosen to become righteous, but he did not. Unless he was given that opportunity, God would not know. Cain had to choose.
That is how I see it, and it is not a limitation to God’s omniscience, because He has all moments within His eternal vision. Also, in knowing us totally He knows that we can choose or not choose Him. We have been granted that gift: participation in the creation of our destiny.
In His omnipotence, He allows us to sin, in order that we may truly free in demonstrating our love for Him. Personally speaking a burning lake of fire is not the worst thing, it is having closed the door to God. In my mind the eternal sulfurous fire could be God’s love illuminating our sinful soul.
I am not sure why you ask, " . . . why wouldn’t He?"
This is how it is. Or have we got it wrong?
Are you suggesting God should have gone about creating heaven and hell differently?