To be fair everyone's motives in the game revolve around Noctis. Gladio's objective is to protect Noct, Prompto's is to be his friend and keep him from being lonely, Ignis' is to advise him and guide him, Cor's is to watch over his progress, hell Ardyn's motive is to see Noctis ascend so he can kill him. Not sure why people always single out Luna for this and bash her about it. Also like I said before the premise of her DLC was confirmed Luna's not a very great character to give an episode as she is when alive from a gameplay perspective, she's just too passive and weakened to really show any sort worthwhile gameplay opportunities unless they were to just go with a walking simulator where you just walk all around Lucis forging the covenants which we would only see 2 of before we catch up with her in Altissia. Afterlife Luna is the best place to make her playable since they can explain her suddenly being stronger and more offense based as her gaining new powers as part of ascending as the Chosen Oracle.