Theres acheivements for them. 10 50 100 300 500, each achievement gives a pet/item.

10 -> Title
50 -> Chocobo Baby minion
100 -> Vanity Crown
300 -> Chocobo Barding
500-> Gold Magitek Mount.

Redeem the achievements at the achievement guy in Gridania.

Otherwise they serve 0 use. I have like 11 from running some low level dungeons in duty find. Its nice to get. I ususaly try to give someone who was overall pleasant or helpful mine.