Why?

Because it is better to not laugh than pretend to laugh, it is better to save it all for that moment when you truly feel like laughing loud and hard and deep. When the quiet and calm is comforting don't pretend that solace can be found in mindless chatter that's supposed to be entertaining. If you are the company you prefer, then choose yourself. Let the world call you gloomy and serious. The world doesn't know.