People here keep a poker face on the street, will not take the initiative to chat with or help unknown pedestrians, and feel it`s OK to yell at customers. Why? My theory on this perceived rudeness goes back to religion.
Most Russians attend just a few, if any, church services a year. They have no history of growing up an active Jew or Christian as communism discouraged religion. The Orthodox Church is now established as the traditional faith, gets on the news just about every night... but its moral instruction hasn`t taken hold.
Few people here know the stories of the Good Samaritan, the Prodigal Son, or the Sermon on the Mount . Beyond city center there are few church bells, no moral instruction from Hebrew or Sunday School, no weekly sermons emphasizing how important it is to be actively kind to your family, neighbors, and especially to strangers! I was an active Presbyterian back home, even though I am an agnostic. It was good to get moral reminders every week and be part of a caring community.
The West has many centuries of Bible centered religion, while here the church is top down. They are unlikely to recruit parishioners for choir, clubs, church dinners. It seems they often have no idea who you are and do not care.
If you meet with rudeness in Russia I believe it is because Biblical moral instruction is lacking. Without this education, the people see their behavior as acceptable.