Clearly someone needs to be able to handle crisies, but that someone does not have to be a shaman. Why not choose the cook or the medic?
Because crisis intervention and suicide prevention are not usually incorporated into the curricula of the Cordon Bleu academy. Nor are they incorporated into the training given to your normal E-4 mess sergeant. They're not even part of the standard EMT package (although some paramedics get it as part of their training).
They are, however, part of the standard seminary curriculum.