If you’re talking about a NOISY muffler, it serves to protect the integrity of genetics in the human race, by serving as the opposite of a natural mating call.
You see, when females of the human species hear a fart-can exhaust on a Civic, their drive to mate and propagate the species dries up and stops completely, so they don’t risk having offspring with the owner of a vehicle like that- who so clearly doesn’t have enough genetic value to produce offspring that promise to be worth anything.
It’s a natural phenomenon also observed in the presence of “truck nutz” or racing stickers on cars that have never raced.