It's good to greet others on public transportation.
Pat is traveling across town to get to the mall.
Pat wants to have an enjoyable ride on the bus on the way there.
Pat sits down and greets the person after they say hi.
Pat sits down and the person sitting next to him says hello and Pat ignores him.
The two have a pleasant conversation and have a lot in common.
The entire ride on the bus is now awkward and nothing gets said.