Players often lose morale if they are benched, or even at the start of new day. Your benched players may not need as high morale as fielded players. Some managers play team with low morale (or low condition), we don't know exactly the effects.

And remember, using 2 morale packs on a player at once will raise from any status (very poor, good, etc) to superb. Just like maximum 15 medical packs will fully heal any length injury.