I mean we have countless Reddit stories where someone’s dog died that day, and while groceries shopping someone tells them “hey, a beautiful girl like you should smile”.

That’s just an a**hole move. You don’t know anything about that person. Maybe they’re not smiling for a reason. I’d say it is very likely that this might be the case… Otherwise they’d probably already smile… And people keep forcing themselves on other people and telling them what to do. Like smile. When it’s really none of their business and very intrusive.