why do you think that no new songs were being added to the old songs of kinos people

Kino's people are indigenous Mexicans. They are native to the land that was conquered and colonized by the Spanish many years before. The subtle implication of this particular excerpt in the book is that several centuries of Spanish colonial influence have gradually eroded the indigenous culture. Kino can still sing the old songs; they provide him with a vital historical and spiritual link to his ancestors. Songs are thus a very important part of Kino's culture. Through them, memories of the dim and distant past—Mexico's pre-colonial past—have been passed down from generation to generation, enabling indigenous Mexicans to keep fragments of their heritage alive. But no new songs have been added to the available repertoire due to the homogenization of Mexican culture after centuries of Spanish influence.