The biggest product that Domino's sells is not pizza. It is a flag that says "Domino's" that is bought by the people who own the franchises. Domino's competitor is not mom&pop pizza. It is McDonalds/Subway/Arbys/etc

So Domino's provides the backend support + marketing + development and for that it gets a hefty fee from whoever attaches Domino's flag to the location.