I'm wondering if franchising has something to do with this. There are just so many fast food restaurants along the highways and dotted around the sprawl of big box stores that surround towns these days. And they seem to always be nearly empty.

My (wild) guess is that some of this is that the motherships are permitting overbuilding. They get their franchising fees regardless, and don't necessarily have a whole lot of reason to care if their franchisees are bringing in enough business to turn a healthy profit.