Heck, they don't do midwest either. I remember they did a baseball game for charity in North Carolina several times, but always in summer. They sometimes get 1 or 2, maybe 3 to appear somewhere unusual sometimes.....
There used to be a huge Days day in Salem, Illinois for several years, and they would get a whole big group of cast to come. But the person who organized it went off the board Chamber there, and no one else wanted to tackle it. (And yes, I wrote to inquire, as I really thought a lot of Spectator members would have loved to arrange something.) Salem is in central Illinois, about 60 miles east of St. Louis.
But the event in Burbank is free to the public, there are NO travel expenses to get the cast members there, (Planes, hotels, etc.) so can understand why it is so big.