Why is the inclusion of Aeneas in the Iliad historically significant?

In Book XX, there is an unduly long episode recounting a confrontation between Achilles, who has rejoined the fight after the death of his companion Patroclus, and Aeneas, a prince of Troy but from a minor branch of the Trojan royal family. Poseidon has prophesied that Aeneas will survive the Trojan War, and Virgil, in the Aeniad, has Aeneas not only surviving the war but founding the Italian (Roman) nation and the family of Julius Caesar. As Malcolm Willcock has pointed out in his Companion to the Iliad, Homer may have included this episode to honor a family, in Homer's time, who claimed descent from Aeneas. External evidence of the Aeneas story may have been supplied by the Greek-Roman historian and geographer Strabo in his now-lost Historical Sketches. More important from a literary perspective, however, is that this episode may indicate that Homer was a court poet, dependent on the support of the court to which he was attached.