There are all these different iPhone and iPad models now but I believe it is in Apple's interest to differentiate with niches and follow Tim Cook's reusing of parts. It is an enormous market. I don't buy that there's no scope to have a size other than large and extra large.
With slowing sales, maturing tech, Apple's stated emphasis on services and a high risk of pricing iPhones out of their own market with the XS/XR, there needs to be as many entrances into the Apple garden as possible. Millions and millions of people cannot afford these prices with the XS/XR, yet they have had iPhones in the past and are attracted. Don't alienate them.
With slowing sales, maturing tech, Apple's stated emphasis on services and a high risk of pricing iPhones out of their own market with the XS/XR, there needs to be as many entrances into the Apple garden as possible. Millions and millions of people cannot afford these prices with the XS/XR, yet they have had iPhones in the past and are attracted. Don't alienate them.