First, tomatoes need pollinators. By making your garden plot attractive to them, you can up your tomato success ratio with natives that can flower all through the growing season and beyond. And, CA natives can subsist on very little water, happily using the leftovers from what your plants don't use. Second, planting natives makes a pretty garden -- a very practical concern when living in urban/suburban areas with neighbors who frequently want pretty. Third, planting natives is a wonderful, cheap way to "tithe" to the environment, and a healthy environment goes along with healthy eating.
One of us created the garden in the picture, which was a neglected, ice plant-choked patch in a town-house complex in Pleasant Hill. It is now filled with California natives, plus some non-invasive drought-tolerant plants from other parts of the world. (The homeowner's association would not allow edible plants). It took 2.5 years for it to get this way. Starting from the top left of the picture, the CA natives are: California fushcia (Zauschneria sp.), foothill penstemon (Penstemmon heterophyllus), deer grass (Muhlenbergia rigens), coyote bush (Baccharis pilularis), and Idaho fescue (Festuca idahoensis). There is a young Howard McMinn manzanita (Arctostaphylos "Howard McMinn") barely visible, just in front of the gallardia and lavendar.
This is a simple example of what you can do -- for your tomatoes, for your environment, and ultimately for you.