Fundamental economics. There is a reason that California is a major grape / wine producer .. climate. Farming effectively, getting high yields of quality produce is difficult .. and it is made more difficult if you try to operate at commercial levels in areas that have high humidity and don't provide the benefits of warm days and cool nights. The California coastal area is a dry desert .. naturally minimizes plant diseases (still have to be controlled) and gives a better chance for producing high yields of quality crops. Another region very similar is the Peruvian coast ... dry desert coastal region similar to the Salinas Valley in California. It has become a boom region for grapes, asparagus, avocados and a variety of berry crops.
Those warm days and cool desert nights provide a key micro climate ingredient - temperature differential of 15 - 20 degrees. That enables or results in the fruit produced developing a higher brix level (natural sugars), and enhances overall plant vigor and shelf life and quality of the fruit produced. I have been involved in international farming operations since 1975 .. Panama, Colombia, Peru, Guatemala, Mexico, Dominican Republic, and also in California and Florida. For COMMERCIAL production of grapes ... low humidity, dry desert areas with warm days and cool nights are critical. Production in other regions lacking these fundamental micro climate characteristics is non-competitive from either a quality or cost basis.