I am not sure why it took Apple this long. In 2013 and 2014 I wrote how Apple's services revenue would or should be an iPhone subscription model and bundled with Apple Care by default instead of relying on App Store.
Apple doesn't need the immediate cash, as a matter of fact for a long time Apple's problem was that they have too much cash on hand.
It would also allow Apple to put up pricing of iPhone, making the leasing program a lot more attractive.
Unfortunately this is US only.