I remembered another (though I forget where I saw it pointed out): a lot of games have equipment that can only be used by certain characters. Maybe only archers can use bows, or clothing is restricted by gender, or whatever. Yggdra Union is a Sting game, so of course it’s going to do this in a more complicated way than most. For example:
Milanor can’t read, so this book is no good to him.
But why is it that headgear can’t be equipped by Rosary specifically?
Well, she already has a better hat.