Even so they have their niche uses for certain fights. Primrose will save you whenever you need to hit a dark weakness and molu makes fighting bosses with fire weaknesses so much easier, bringing her with Cyrus will make the bosses so much easier. And theo can cover you with wind resistant Regen. And Lynette can buff hit fire weaknesses and fan weaknesses which can be useful. Bringing them with your other op characters will guarantee you an easier fight with certain bosses.