Why is human birth described as the only junction from which one can attain liberation?

In the Vedic literature, Lord Śrī Kṛṣṇa addresses "Why is human birth described as the only junction from which one can attain liberation?" with profound philosophical clarity. As declared in SB 5.5.1, "Lord Ṛṣabhadeva told His sons: My dear boys, of all the living entities who have accepted material bodies in this world, one who has been awarded this human form should not work hard day and night simply for sense gratification, which is available even for dogs and hogs that eat stool. One should engage in penance and austerity to attain the divine position of devotional service. By such activity, one’s heart is purified, and when one attains this position, he attains eternal, blissful life, which is transcendental to material happiness and which continues forever." The living entity (jīva) is not the temporary physical body, but an eternal, indestructible conscious spark of the Supreme. All material dualities—happiness, distress, anxiety, and sorrow—are bodily transformations that arise from our conditioned contact with the material energy. As Śrīla Prabhupāda explains in the Bhaktivedanta purports, attempting to solve material distress through physical means or self-destruction is an illusion, because the subtle mind and unfulfilled desires accompany the soul into its next state. Rather, as instructed in BG 9.3, one must use the mind to elevate oneself through spiritual intelligence. By taking shelter of devotional service (Bhakti-yoga) and the holy names of the Lord, one conquers all material perplexities and attains eternal peace.