Hunts allow you to buy better stuff at the clan's shop. Some hunts open access to some optional Espers (the aeons of XII) and other areas in the game that you will not see without them.

You are not nearly at the first 20% of the game let alone "half done"

Fran isn't invisible, she will show quite a lot a bit later, when you get to Golmore Jungle. But to see her now just make her your party leader. You know how to do that, right ? If not, take all from the party but her, then add 2 people back. Presto, Fran on all screens