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.
What worries me is that this spells further price increases across the lineup, and the leasing option is serving as a way for consumers to be able to stomach the ever increasing price of RAM. There's going to be a limit to how expensive these products can be before sales start really suffering and moving to hardware-as-a-service extends that runway even further.