Because, let's face it, you're not going to be a functioning member of society if you don't know when to use a napkin.
Learn the proper way to eat a salad, use a fork, and not touch the queen's face.
Master the art of saying "please" and "thank you" without losing your mind.
Don't be the person who gets invited to the party and then eats the last donut. Learn to hold the door, say your apologies, and not be a jerk.