That's not an explanation. You could say that about a thousand things in McDonald's business. They are all a relatively small part, but in fact McDonald's has an army of people optimizing them all, and they are overall very successful.
Why do you think they would be able to abuse any of the operators? There are dozens and dozens of fast food franchises in the US, all in cut-throat competition. You may have heard of McDonald’s, Burger King, Wendy’s, Subway, KFC, Chick-fil-A, Domino’s, Pizza Hut, Dunkin’, Sonic Drive-In, Popeyes, Little Caesars, Arby’s, Chipotle, Dairy Queen, Jack in the Box, Hardee’s, Panda Express, Jimmy John’s, Five Guys, Wingstop, Culver’s, Zaxby’s, Raising Cane’s, Whataburger, Bojangles, Shake Shack, El Pollo Loco, Firehouse Subs, Jersey Mike’s, Del Taco, Checkers, Rally’s, Church’s Chicken, Moe’s Southwest Grill, Qdoba, Captain D’s, Freddy’s, Tim Hortons, Smoothie King, Blaze Pizza, Baskin-Robbins, White Castle, Portillo’s, Noodles & Company, Schlotzsky’s, Tropical Smoothie Cafe, Auntie Anne’s, Marco’s Pizza, Boston Market, Smashburger, Fuddruckers, WingStreet, Krystal, Papa Murphy’s, Hungry Howie’s, The Habit Burger Grill, Jamba, Nathan’s Famous, Steak ’n Shake, Waffle House, Big Boy, Pizza Ranch, Cook Out.