Every culture has norms. The norms are amoral, meaning that they are neither moral or immoral in of themselves.
Norms associated with obligation can be particularly tricky because once entered it is often difficult to exit as it would be considered rude.
So, if I say hello to you, this opens the door to an obligation of always saying hello. Now this is not always the case, but sometimes it is and when it is it can create a sticky situation for the person who simply does not want to be bothered. I know enough people, one could say to oneself, and thus I don’t really need to know you. Saying hello opens this door I just don’t want to. There are many situations, like commuting to work, where you just want to be alone and not engaged in conversation with someone with whom no real relationship will develop. The thoughts on this path can go on and on and on.
What is the answer?
For do I now persuade men, or God? Or do I seek to please men? For if I still pleased men, I would not be a bondservant of Christ. (Galatians 1:10)
When we please God we are set free from the cultural norms. We gain access to guidelines of when to cross them for the glory of God.