God granted it because Job was to be a world example, for all time, of God's protection and goodness. That took place only once in history. God, my Father, is not about to give Satan liberty to touch me or any other believer. The danger is when the believer lets down his guard and enters into unrepented willful sin. Then there is a breach in the hedge for the enemy to come in.
Willful sin is like grabbing hold of the tail of a scorpion.
The believer grieves over both general and personal evil. We long to be free. We want God's Kingdom to come. But victory has already been won at the cross. The devil is defeated and salvation has come.