My take...
BGT/SWF and IOA/USF draw more locals.
If the USA goes to war and people are scared to fly, the locals will still visit the Orlando parks keeping their attendance figures stable.While Disney's attendance drops and they blame it on recession/war.
Disney has some specials for Florida residents, but they're still higher than Busch and Universal.
Plus it goes back to my take on having to visit 4 parks to do all the rides, versus 2. For the guests flying in and spending a week, that's no problem. But for myself, I don't have time to hop thru 4 parks when I can get it all at IOA/USF with 2.