As far as the stated reasons as to why God will judge the human race, the Bible has the following to say.

1.  Reveal The True Character Of Everyone

Judgment will reveal the true character of everyone. Jesus said.

So have no fear of them; for nothing is covered up that will not be uncovered, and nothing secret that will not become known (Matthew 10:26).

But I tell you that everyone will have to give account on the day of judgment for every careless word they have spoken (Matthew 12:36).

Paul wrote.

the work of each builder will become visible, for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each has done (1 Corinthians 3:13)

2.  To Give Public Reward Or Punishment For Deeds Done

Judgment will be public. Everyone will publicly be rewarded, or condemned, for their conduct here upon the earth.

For the Son of Man is to come with His angels in the glory of His Father, and then He will repay everyone for what has been done (Matthew 16:27).

Paul wrote.

For He will repay according to each one's deeds: to those who by patiently doing good seek for glory and honor and immortality, He will give eternal life; while for those who are self-seeking and who obey not the truth but wickedness, there will be wrath and fury. There will be anguish and distress for everyone who does evil, the Jew first and also the Greek (Romans 2:6-9).

3.  To Vindicate God's Righteousness Toward Humanity

Ultimately, judgment will vindicate the righteousness of God.

After this I heard what sounded like the roar of a great multitude in heaven shouting: "Hallelujah! Salvation and glory and power belong to our God, for true and just are his judgments. He has condemned the great prostitute who corrupted the earth by her adulteries. He has avenged on her the blood of his servants" (Revelation 19:1-2).

When all the facts are in, God's judgment will be shown to be fair and just.

Summary

The purpose of God's judgment will be to show the true character of each person, to publicly reward or punish each one for their sins, and ultimately to vindicate the righteous character of God.