Florida is a ling weekend, To justify going out to Dulles to fly to Arizona, would mean a real vacation, and for a lot of fans that isn't worth it
It works on the flip side as well.
Just using myself as an example, it's a full vacation from California to Florida. Not necessarily worth the time or the cash for me to do it.
In Arizona, it's a long weekend, or even multiple weekends. I know Id have six or seven friends with me on each trip. It's only 5-6 hours away.
With Strasburg and Harper, you'll probably find a lot more casual fans on the West Coast interested in going to check them out as well.
