North Koreans are too busy making sure they survive, along with their families, which is why kindness is rare there. The man and the entire train could be punished for helping Mother evade the ticket inspector and break the law, which would very likely be considered disloyalty to the state and the Kim regime. However, the fact that Mother, Min-ho, and Hyeonseo encounter such kindness suggests that it isn’t as rare as they may think; it’s just not always obvious under such oppressive conditions.