Linked from
The 8 pages that link to Gathas, each with the reason it gives.
AvestaBroader topic: These hymns are the Avesta’s oldest and most authoritative poetic layer.
Ahura MazdaBroader topic: They are the oldest surviving texts that address Ahura Mazda directly.
AvestanBroader topic: Their language is the oldest and most archaic form of Avestan.
MazdaismBroader topic: They offer the closest textual access to Zarathustra's religious teachings.