John Owen gives his answer in Vol. 1 on his commentary on Hebrews, in Part 2, Excercitation VII.14.
Preliminarily, Owen establishes that God may have justly rescued angels from their sin, but that justice does not obligate God to do so. While the same could be said for God’s redemption of man, there is such a difference between the original transgressions of angels and men that God’s righteousness is more gloriously displayed in withholding rescue from one, and that this reflects good concern for God’s glory being displayed in universe.
1. Angels were created in a higher state than man, in the highest heaven, while man was placed on earth. Earth is good and suitable to man, but not as glorious as heaven.
2. In heaven angels were tasked with attending the throne of God, to minister to him, give glory to him, to execute his commands of providence, all of which together are the highest honors given to creatures. Man was given the duty of cultivating the ground, which while good, is below the vocation of angels.
3. Angels enjoyed the immediate presence of God without a mediator resembling themselves. Man was kept at a greater distance and without such direct communion with God.
At this point Owen affirms that this does not excuse the grievousness of man’s sin, but greatly aggravates the wickedness, ingratitude, and pride of the angels…