Gravekeepers don't need to know anything else, as long as they know how to guard graves.
But if one day the tomb collapses, what should the tombkeeper do?
"Sir, are you going to buy something without paying for it?"
"Isn't that one for burning?"
"Sir, you are joking. Of course the money is used to buy things."
"Huh? Okay, here..."
"Ming, Ming coins?!"