Native flora brings native fauna. Not only does this mean habitat for human-appreciated critters like birds and butterflies, but more invisible and possibly more important creatures such as insects. California, for example, has nearly 1000 species of bee, many of whom have a single plant species as their nectar source. The need for pesticides disappears. On a higher level of the food chain, small mammals also return.
More gophers mean more owls, etc.
When native plants are growing together in their own plant community configuration, without fertilizer and cultivation, the soil regains its health. Everything from earthworms to beneficial bacteria return. Perhaps the most overlooked consequence of using native plants is the esthetic benefit. And finally, on this very short list culled from a very much larger one, consider the impact that growing native has on the human heart and spirit, something I've learned a lot about in the course of publishing Growing Native. If a visit to a park or other natural area is perceived as beautiful and spiritually refreshing, imagine what happens to people who actual participate in the healing of a patch of earth.