You'd be surprised. Kids want McD's, not some random burger restaurant. They want the real thing. This value proposition exists with any restaurant with franchises though. It isn't specific to McD's. According to my wife (who fancies burgers), Burger King is way better anyway. I wouldn't know. For me, it is a scam. Since what they sell as cheddar isn't cheddar (it has nothing to do with that) but processed cheese.
Going back to my original point, kids don’t eat McDonald’s for every meal, or even 10% of their meals.