Apple Upgrade requires AT&T, T-Mobile, or Verizon — here's the likely reason

Apple's Upgrade program requires customers leasing an iPhone to connect to AT&T, T-Mobile, or Verizon at enrollment. John Gruber of Daring Fireball suggests this is likely due to financial and legal requirements tied to the leasing model, with the carriers needing to be party to the arrangement for the program to work. The fine print has drawn attention from users and analysts.