I'd imagine they're getting a kick back from the carrier of choice to offset the zero percent financing. It sounds like you can still switch carriers without worrying about having the phone unlocked, like a subsidized phone used to work in the U.S. They are just banking, quite literally, on someone sticking with whatever carrier that person chose when they bought the phone. Regardless the reason, I find this annoying and I rather pay up front for a "non-carrier specific" version than play into these games. I'll likely not even use my Apple Card for the purchase in hopes that if enough people reject this ploy of theres that they'll change back.