Everything about this is highly contextual and varies across cultures. Smiling in some situations makes you look powerful, in many others it makes you look weak. Being very animated can make you look carefree in some situations and just wild in others.
The more time I spend in cultures that I didn't grow up in, the more convinced I become that there just aren't any universalities in this direction. Any attempt to do so is to try to generalize over all human behavior and the effort will either be wrong, being that there will be some cultures or situations where the rule doesn't hold, or it'll be useless, essentially telling you what you already know.
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".
South-East Asia:
It's okay if you're trying to be friendly with a regular guy but if you're trying to get someone to work for you then you'd be better off not smiling and exchanging pleasantries or they'll rip you off.
"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.
There are a lot of examples of the differing meaning of a smile when you google it. Sometimes it is simply not appropriate to smile. I'm not sure if there are any culture that sees them as entirely evil, but a few do have a concept of an evil grin, a concept that sits alongside the smiles being friendly. It doesn't seem to be a stretch that a mistimed smile might make you look like a loon and other such differing beliefs.
Of course, when someone tells you his mother died and you smile like an idiot, it surely will not create a positive effect.
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.
It is still a sign of happiness there. Only these people do not believe that one can be happy all the time so constant smiling comes off as insincere.
There is a Russian saying "Смех без причины - признак дурочины" — smiling without a reason is a sign of stupidity.
The more time I spend in cultures that I didn't grow up in, the more convinced I become that there just aren't any universalities in this direction. Any attempt to do so is to try to generalize over all human behavior and the effort will either be wrong, being that there will be some cultures or situations where the rule doesn't hold, or it'll be useless, essentially telling you what you already know.