When grandparents in a household wake early and sit for prayer, the grandchildren absorb that rhythm without being taught. When a teacher arrives on time every day, the students gradually do the same. Actions speak in a frequency that words cannot match.
Krishna's point is direct. People in positions of influence — parents, teachers, leaders, elders — set the tone for everyone around them. Whatever they do becomes the pramana, the yardstick. Others copy it, consciously or not.
This is why Arjuna cannot simply walk away from the battlefield. He is a prince, a warrior of the Kuru dynasty. If he abandons his duty, countless others will take it as permission to abandon theirs.