Longer answer: McDonald's has chosen to optimize for total revenue, while Chick-fil-A has chosen to optimize for something more like ROI on each store. This is a direct consequence of the different franchise models, where McDonald's takes a cut of sales and doesn't have an ownership stake in each location, while Chick-fil-A take a cut of both sales and profits, and has ownership of the physical location.
As dave5104 mentioned, there are over 14,000 McDonald's locations in the US vs around 2,000 Chick-fil-As. McDonald's has saturated the market to the point that individual McDonald's locations cannibalize the sales of other nearby locations.
For example, there are 14 McDonald's locations within a 5-mile radius of where I live. If you closed down half of them, total revenue would probably drop some, but not anywhere near half. Many people who wanted McDonald's would just travel a little bit further to get to one. As a result, per-store revenue would go up. Per-store profit would go up by an even greater percentage since there are fixed costs per location. And if you closed the right number (which might be more or less than half), total profit would go up as well.
This would be great for franchisees, but from McDonalds' perspective it's worse since total sales would decrease, and that's what they're getting a cut of. Chick-fil-A's model, where they take a cut of both sales and profits aligns their interests more with their franchisees.