Just because in 5-6 years even best of the best fade versus cheaper new base models. Lots of people bought 12PM because it was separated by a camera - base iphone 13 inherited camera directly from 12PM.
13PM again had better camera than 13P - Iphone 14 has the same camera from 13PM.
Iphone 12 lived 5-7 hrs from battery, now iphone 13 mini does the same, while 13 pushes further up to 9 hrs.
The same works in Macs - $50K Mac pros on intel are now losing to $800 mac minis. There is no need to buy a phone for 5-6 years by opting for the best - bests will fade away really fast.
If person just tends to hold any of their phones for 5-6 years, then that is another story.