@voronesh234 @Bead @Granwalder @NailBomb @matrix If you ever find yourself in a western country, the American South especially, you can get by on not smiling but you have to interact in other ways when someone smiles at you. Wave and nod, smile back for a few seconds, say hello, something.
You don't have to smile 24/7, no one does that, but if someone smiles at you and you don't return the gesture somehow they will think something's wrong, either you're upset because something terrible just happened to you, aren't paying attention or you are angry at them.
I say American South because I've seen stone faced yankees come down here and be both quiet and unexpressive and generally the reaction when they leave is "What are they so mad about? Did I do something to piss them off?"