Why plant natives?
Native plants are generally easier to care for, support biodiversity, attract wildlife to your yard, and don't cause the problems associated with introducing exotics like the Bradford Pear.
Being easier to care for, watering beyond establishment is rarely required. This cuts down on your water bill as well as well as conserves water. Native plants grew in our native soils, so fertilizer isn't needed if you're following the guides of "Right plant, Right place."
They support biodiversity by planting many species or even a single species that attracts or hosts many different species. Planting a White Oak, for example, will support over 400 species of insects including butterflies and moths. Their acorns feed birds and mammals such as deer, squirrels, fox, woodpeckers, bear, chipmunks, turkey, etc.
Keeping with planting native to your area prevents the problem of introducing invasive plants, which leads to habitat loss and decline in populations of native flora and fauna. While some of our natives can be a bit aggressive, they are usually kept in check by our native wildlife.