My friend has had her phone for 7 years and she's being pushed off it because apps are refusing to run on it now. No other reason than that.
Once that is done, it works fully as expected. I dread the day some new version will fully block it.
I can't reinstall a small stupid clock app I've found once (it had decimal, French revolutionary, hex, Roman format, star trek time and date) on my iPhone because it's no longer listed in library nor store itself and I didn't ever included it in backups.
It's buried on iPad 1 that cannot boot any more.
BTW The stores requirements are not really about minimum OS version of the phone, but minimum SDK version of the build chain. It's often possible to have secure code path for new OS and the legacy code path for old OS, but in practice it can be burdensome sometimes.
> longer availability of operating system updates, at least 5 years from the date the last unit model is sold