Through much of the narrative, Siddhartha's understanding of the true path is imperfect or compromised. The desire to become a samana doesn't work for him at first; he's a seeker, but something initially is wrong, missing.
Arguably, it is his life in the "real" world that changes him so that he can potentially accept the state of self-denial in which he wishes to live. The central point in his journey is his worldly existence as a man in business, as the lover of the beautiful courtesan Kamala, and as a father, though this last role only comes to him later on, and unsuccessfully.
Siddhartha cannot know the meaning of om or Enlightenment until he has experienced what 99% of the world's population believes are the things that have genuine meaning: love, family, and money. One would think the implication of this is the opposite of the exalting of the spiritual world that is at the heart of Hesse's theme. And in some sense, it is exactly that.
What makes most of us as readers, in my view, respond to the novel is the experience in its totality through which Siddhartha journeys. The meaning of his own story is defined not only by what he experiences directly but also by the story of Kamala and their son. Kamala's death is a tragedy on the level of human actions, not the rarefied stratum on which it is Siddhartha's ideal to live. So is the inability of Siddhartha to bond with his son. These things have a primal significance that both contradicts the enlightenment sought by Siddhartha and simultaneously enables it. The enlightened soul, the one reaching the om or "ultimate reality," can only do so by seeing existence as it is outside this essence of the spiritual.