Something that Chick-fil-a does that makes their menu so irresistible is their signature or "original" items. For example, their homemade hand-squeezed lemonade is so delicious. Not only that but it has a unique taste, which makes it exclusive. You can't get it anywhere else.  Chick-fil-a spend time and energy creating this signature drink, and it payed off. Many customers of Chick-fil-a come merely because of the lemomade. I have experienced this during my time at Chick-fil-a. 
Just another thing that makes Chick-fil-a such a profitable and DELICIOUS company!