For Apple devices especially, this is incentivized by the culture around them - a lot of folks just want the newest.
Update the technology on a regular basis as everyone is on a different purchasing cycle.
I guess cars are the same. If you walked into a dealership and all the models had been released 2 years previous you might feel like you shouldn't be paying full price even though you are getting a brand new car.
Arbitrarily lengthening release cycles like this is performative. Particularly in high tech. Doubly so in a category that’s reducing its energy and material footprint.
Consider if we did this for cars. New model once a decade. This would be horrible for fuel economies. To say nothing about safety and EVs.
Based on what evidence?
It will get resold and reused.