Hotel brands force hotel owners to use only certain vendors, taking a kickback from the vendor. Same with restaurants/etc.
I can give a specific example. Roughly 8 years ago, IHG hotels required all of their branded hotels to only sell Coca Cola products. The only reason this would happen is if Coke paid IHG.
It has nothing to do with a person’s hotel stay. It just restricts hotel owners and hotel guests from being able to sell and buy their preferred products, such as Red Bull or Starbucks or Pepsi/Tropicana, for the benefit of Coke and IHG.