Here's why:
* The Azure Flute is required to access the Temple of Sinnoh. This temple is the only location where Arceus can be found.
* The Azure Flute is obtained by completing the main story of the game. You need to complete the game's narrative and achieve certain milestones before the Flute is given to you.
Therefore, getting the Azure Flute is an essential step in your journey to encounter and catch Arceus.