It's not just carriers that enjoy locked phones. Currently, BestBuy (the 2nd largest electronics retailer in America, after Amazon) can only sell unlocked iPhones that are at least a year old. If you want a shiny new iPhone 16 Pro that's unlocked, you have to purchase it from Apple directly.
I don't see this as Best Buy's preferred situation, rather they really need to bring people into stores and this is an agreement with carriers to give them preferential treatment regarding access to their registration systems
