Apple has trouble selling new phones because its old phones are too good. Unlike Android phones, which become obsolete rapidly, iPhones just keep on keeping on.
The main reason I chose to upgrade this year is because I got tired of lugging around a big-ass iPhone 7 Plus. If I’d gone instead for the iPhone 7 two years ago, i’d still be using it.
I still see many people using phones that appear to be the iPhone 6. That’s a four-year-old phone.