Why are worldly relationships considered unreliable for achieving spiritual goals in contrast to the Guru?

The scripture suggests that worldly relationships are ultimately transient and cannot be fully relied upon for attaining one's spiritual goal. Chapter 45 explains that while family members like a mother, father, or son will show affection, their interests are often tied to worldly matters, such as a son looking at the wealth he can claim. Even a wife's grief is described as crying for her own status (widowhood). The text concludes that none of these relations are a true companion in the spiritual goal. Upon final reflection, only one's own self, guided by the Guru who is the embodiment of the eternal Brahman, remains as the means to achieve liberation.