As an American I find it strange that it is ingrained in Russian culture to not smile. So in order to better understand why and how I did some research. Below is what I found out.
The closed-mouth smile: Most often, Russians smile only with their lips, only occasionally showing the upper row of teeth slightly. Revealing the top and bottom teeth is considered vulgar, as it resembles that of a horse.
The servants smile: In Russian communication, a smile is not a signal of politeness. Russians consider a perpetual polite smile an “servant’s smile.” It is considered a demonstration of insincerity, secretiveness and unwillingness to show one’s true feelings.
The non-smile: In Russian communication, it is not acceptable to smile at strangers. Russians smile mainly at people they know. This is why salespeople do not smile at shoppers.
The responsive smile: Russians do not automatically respond to a smile with a smile. If an acquaintance responds to a smile with a smile, this is considered an invitation to come over and start a conversation.
The smile as a symbol of affection: A Russian smile demonstrates to the recipient that the smiling person has personal affection towards him or her. A smile directed at a stranger may elicit the reaction, “Do we know each other?”
The official’s non-smile: Among Russians it is not acceptable to smile while performing one’s job or any important business. Customs agents do not smile because they are occupied with serious business. This is the same for salespeople and wait staff. It is not acceptable for children to smile in class. One of the most common remarks Russian teachers make is, “What are you smiling at? Write!.”
The genuine smile: In the Russian collective consciousness, there is a rule: the smile must be a genuine reflection of a good mood and good relationship. In order to have the right to smile, one must truly like the person in question or be in a very good mood at the moment.
The smile with no reason: If a Russian person smiles, there should be a good reason behind it – and everyone should know this reason. If the reason for a smile is not clear, Russians may worry about the reason behind it.
The appropriate smile: The other people present must consider the smile to be appropriate for the context. It is not acceptable to smile in a difficult situation or if there are people around with known serious troubles, or if someone is ill or preoccupied with personal problems and so on.
A laugh as a smile: Among Russians there is a blurred line between a smile and laughter; in practice, these phenomena are often the same and are likened to each other. Russians often say to people who are smiling, “What’s so funny?”