God's plan of salvation for us is faith based. That means our salvation is rooted in the depth of our faith.
Angels stood in the very presence of God and rejected him. THAT alone is why there is no place for them in God's plan of salvation.
James tells us that "Devils believe and tremble." But "believe" is not faith. It is a simple matter of "seeing is believing."
BUT
The saints believe without sight, and THAT is faith, grounded in hope, of the things promised by God, whom we have not seen.