As with a lot of technology, the iPhone has reached a plateau. There is countless versions of software that are the same, mostly making improvements that hold little to no value to end users.
Just as one “bought” music before the advance of streaming services, we now have to “subscribe” endlessly to listen to music or watch movies. Why allow anyone to buy anything once, if you can get them to subscribe to something forever to enjoy it? Guessing one can do this already with hardware, but i’m sure we’ll be forced to rent our hardware in the not to distant future as well.