What might be Homer's purpose in having Zeus recall in such detail the story of Agamemnon, Clytemnestra, Aegisthus, and Orestes?

In the hall of Zeus on Mount Olympos, all the gods but Poseidon gather and listen as Zeus reflects upon the moral failings of mortal men. He brings up the example of Aigisthos, who killed Agamemnon and stole his wife, though the gods warned him that Agamemnon's son, Orestes, would someday retaliate - which he justly did. Athena speaks on behalf of Odysseus, pleading with Zeus to free him from Calypso's grasp. He agrees, and the god Hermes will be sent to Calypso to ask her to free Odysseus.