Friend of mine used to manage one. She said that a large portion of her business didn't even involve patrons at the restaurant. She sent several hundred sandwiches a day to be sold at the local hospital, and did a lot of catering-type things as well.
I'd love to get invested in one, those places have a license to print money.
They also sell a LOT of chicken biscuits at schools. My kids would save part of their allowance to buy one on Chick Fil A day.