Silverware is typically only used by unicorns. By the time any other pony managed to manipulate it properly with their hooves they likely would have made a mess of their food, and if they used it with their mouths they couldn't very well eat the food on the utensil.

So when the Cutie Mark Crusaders start discussing amongst themselves the meanings of their classmates cutie marks they come to a puzzle in Silver Spoon.

What is an earth pony doing with a cutie mark of something she can't effectively use?

Edit: Featured on January 4th 2018! I shouted with joy.

Thanks for Alias_the_J and Cosmic Eclipse for edits.