Common people are more influenced by the living examples of great men than by the abstract teaching of the scriptures. Man is a social animal. He is also an imitating animal. He takes his ideas of right and wrong from those whom he considers his superiors. The examples set by the leaders are implemented by the followers. As is the quality of leaders, so will be the quality of the followers. Whatever the persons in authority do, the subordinates imitate.
Sri Krishna implies that if Arjuna were to abandon his duty to act, then the entire community will follow the low standard of retreating from action set up by him which will lead to general social decadence. The Lord cites Himself as an example for Arjuna to act.

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Yat yat, [This is according to the Ast. The G1. Pr. reads, yat yat yesu yesu.-Tr.] whatever action; a sresthah, superior person, a leader; acarati, does; itarah, another; janah, person, who follows him; does tat tat eva, that very action. Further, yat, whatever; sah, he, the superior person; kurute, upholds; as pramanam, authority, be it Vedic or secular; lokah, an ordinary person; anuvartate, follows; tat, that, i. e. he accepts that very thing as authoritative.

‘If you have a doubt here with regard to the duty of preventing people from straying, then why do you not observe Me?’