As factually stated by Nanda Mahārāja, Gargamuni, being a devotee, had no needs. Similarly, when Kṛṣṇa comes He has no needs, for He is pūrṇa, ātmārāma. Nonetheless, He descends to this material world to protect the devotees and vanquish miscreants (paritrāṇāya sādhūnāṁ vināśāya ca duṣkṛtām (B.G.4:8). This is the mission of the Supreme Personality of Godhead, and devotees also have the same mission. One who executes this mission of para-upakāra, performing welfare activities for people in general, is recognized by Kṛṣṇa, the Supreme Personality of Godhead, as being very, very dear to Him (na ca tasmān manuṣyeṣu kaścin me priya-kṛttamaḥ (B.G.18:69). Similarly, Caitanya Mahāprabhu has advised this para-upakāra, and He has especially advised the inhabitants of India:
bhārata-bhūmite haila manuṣya-janma yāra
janma sārthaka kari' kara para-upakāra
"One who has taken his birth as a human being in the land of India (Bhārata-varṣa) should make his life successful and work for the benefit of all other people." (CC.1:9:41) On the whole, the duty of a pure Vaiṣṇava devotee is to act for the welfare of others.

(Srimad Bhagavatam-------10:8:4-------purport).