This is a subject that can be interpreted widely, and one on which I will expect much criticism, response, and opinionated reasoning.
As is commonly known, the poetic art form started out as an oral tradition. This created a catch twenty-two, as nothing is capitalized in the spoken word. This may send shudders through the spines of grammar gods, but never fear because capitalization stems from the necessity to emphasize particular words or phrases on paper that were accented by the speaker that the stories were taken from. All of the thought, timing, and organization in stories was done with singer’s voice; the full stop of the period, the pause of the comma, the excitement of the exclamation point, and the emphasis of the capital.