Look at the constituent parts of an iPhone SE:
https://d3nevzfk7ii3be.cloudfront.net/igi/cDmVFvtAKTZvjOBk.h...
An upgrade necessarily includes a new logic board and likely a new camera module. Once you're disassembling it, you'd inevitably be swap out the battery too. Most of the remaining parts have a distinctly limited service life—in particular the battery, physical buttons and connectors.
The front glass assembly with LCD screen might have a long theoretical life but these do deteriorate over time, they get damaged easily and replaced fairly often.
After excluding the above, there's not much left to salvage—mostly aluminium parts like the outer casing, and aluminium is already one of the most recyclable components of a phone anyway.
So there's really no point.
I’ve speculated this is perhaps more practical on newer laptops (e.g. 2016- MacBooks) where ports have consolidated to just all usb-c and presumably stay that way for longer than a typical 3-year physical design cycle.