Why does God allow Satan and his demons to continue to do evil on Earth?

Why does God allow Satan and his demons to continue to do evil on Earth?

1) To maintain humility in our lives (2 Corinthians 12:7)

2) To develop faith and righteousness in our lives (James 1:12, Peter 1:7-13, 5:8-9, 2 Peter 1:4-9)

3) To bring about trials whereby we can be rewarded when we overcome (1 John 2:13,4:1-6)

4) To teach us how to fight (Judges 3:2)

5) To afflict us in order that we repent (Job 33:14-30, 1 Corinthians 5:1-6)

6) To demonstrate the power of God over satanic power (Mark 1:21-27, 16:17-20, Acts 13:6-10, Ephesians 3:10)