“Social Proof” is a concept psychologists have used for a number of years to explain social interactions: Read More on Wikipedia
General idea is that people tend to look to the actions of others when deciding how to act in a certain situation. So, when people around you are shaking hands as a greeting during a business meeting, you might be disinclined to kiss them on the cheek. However, if you’re in a culture where kissing on the cheek is a proper greeting, and you see people doing it, then kissing on the cheek has been “proven” to be the correct action.