I believe that Nintendo didn't make a game because Farore is the Goddess of Courage and Link holds her part of the Triforce. Link and Farore are of close similarities. Farore looks like a Korki and Link lived in Korki Forest as a child in OoT. Farore wears green and so does Link. In OoS/A, Farore is the Oracle of Secrets which is if you have both games (which I do) there are people who tell you secrets to bring to the other game's Farore. This is why I believe Nintendo didn't make Farore one game 'cause she is like the assistant to the Maku Tree, just like the Korkis are loyal to the Deku Tree.