According to the text, why are worldly relationships like family considered unreliable for achieving spiritual goals compared to the Guru?

According to Chapter 45, worldly relationships are unreliable for spiritual progress because they are often based on self-interest and cannot provide ultimate support. The text explains that while a mother and father show affection, a son will be focused on his potential inheritance, and a wife will cry for her own potential widowhood. It states that no one, whether it be in-laws, sons-in-law, or a wife, can be a true companion in the spiritual goal. In contrast, the Guru is identified as the true Brahman, the eternal reality. Therefore, the text advises that a seeker should give up hope in others and focus their devotion singularly on the Guru to achieve their spiritual aim.