I'd like to know the culture where smiling is seen differently. It is the global symbol of happiness and tells everybody on earth "i'm a friend" or at least "i'm friendly".
"Hey, how are you? How much will you charge to take me 5 kms" would be the wrong approach to take with a taxi driver. Just try to look stoic (but not like an asshole) and you'd be better off.
https://www.theatlantic.com/science/archive/2016/05/culture-... https://blog.allpsych.com/smiling-means-different-things-in-... https://www.translatemedia.com/us/blog-us/the-meaning-of-a-s...
The way I understood OP, it seemed as if - in a normal setting - smiling would be frowned upon when talking to people in general in some places... which I find hard to believe.