This is actually the wrong question, the biblical question is:

How can a holy and righteous God let us live at all?

You see, the Bible tells us that the cause of all the pain and suffering in the world is man's sinfulness and that man is completely depraved; that man's righteousness is like filthy rags; and that every thought and intent of man's heart is wicked all the time.  The Bible also tells us that God is holy and righteous. 

So we have to ask, believing both of these truths found in the Bible, how does this reconcile with us still living at all; let alone experiencing joy, friendship, and any material blessings?  Why has God not judged us already?  Why are we still living? How can God be holy and righteous and not judge us for our atrocities?

God has revealed in scripture his standard of righteousness.  We must love the Lord our God with all our heart, soul, strength, and mind; we must not have any other gods and we must serve him alone; we mustn't represent him by anything created; we must not misuse his holy name;  we should rest one day in seven and keep it holy to him; we must honour our mother and father, we must not murder, we must not commit adultery, we must not steal, we must not lie, and we must not desire anything that is not ours.

God's standard is not as simple as the words of the ten commandments. As we study the rest of the Bible, the depth of his standards as shown in the ten commandments becomes clearer.  The law is not only outward, but also inward.  It is not only sin when we murder, but also when we hate, not only adultery but lust.  The commandments are categories within themselves, not only is lying to a judge in a court of law wrong, but being dishonest in any way, shape or form.  Also, the commandments are not only one-sided - Not only 'thou shalt not lie', but also thou shall tell the truth, not only 'thou shalt not murder', but also thou shall preserve life.  Where we fail in the least, we've failed in the whole.  We cannot keep God's law, because unless we keep it perfectly we have not kept it at all.

So is God unrighteous because he hasn't punished sinners? He did not punish Abraham the liar, he did not punish Moses the murderer, or David the adulterer and murderer... Is God unrighteous in this? NO.   

Why not?
Romans 3:21-26 - "But now the righteousness of God apart from the law is revealed, being witnessed by the Law and the Prophets, 22 even the righteousness of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference; 23 for all have sinned and fall short of the glory of God, 24 being justified freely by His grace through the redemption that is in Christ Jesus, 25 whom God set forth as a propitiation by His blood, through faith, to demonstrate His righteousness, because in His forbearance God had passed over the sins that were previously committed, 26 to demonstrate at the present time His righteousness, that He might be just and the justifier of the one who has faith in Jesus."

God passed over the sins of Abraham, Moses, and David because he would satisfy his righteous judgement through Jesus' substitutionary atonement for all he chose to have mercy on.  While you are still alive, repent of your sins and trust in Jesus for salvation from them. Be grateful that God has allowed you to live this long so that you might turn and repent, and be fearful that if you don't repent, after you die you will stand before God and be judged, as it says in Romans 2:4-6: "Or do you despise the riches of His goodness, forbearance, and long-suffering, not knowing that the goodness of God leads you to repentance? 5 But in accordance with your hardness and your impenitent heart you are treasuring up for yourself wrath in the day of wrath and revelation of the righteous judgment of God, 6 who 'will render to each one according to his deeds.'"  Now is the accepted time. Now is the day of salvation!