Most likely areas where they perform a lot of family separations that can also be close enough to other common locations with many people of color to be a useful training aid. Arizona is close to the south with wide open cities and Chicago is indicative of a lot of northern cities with choose packed buildings. There's already a ton of teaching facilities for individual houses or foreign locations. This is really not that surprising. If they were building something like Minneapolis or Boise I'd take more notice.