"I'm a small business owner!" no, deary, you're just the fall guy for a massive international firm. For a fraction of the profits, you get the privilege of holding all the risk of actually operation a restaurant.
I think they actually get almost all of the profits of the store. The fast food company makes money from the franchise license, rent, and supplying the equipment and food
Technically they could also just increase revenue with better marketing and customer service but we all know they would never try that first over slashing employee operating expenses