The problem I've encountered with several older Apple and Android devices is that the hardware works just fine, and the older version of the OS also works well

The problem I've encountered with several older Apple and Android devices is that the hardware works just fine, and the older version of the OS also works well enough, but more and more apps begin to require a newer version of the OS. When I can't install, upgrade, or use these apps by normal means, the usefulness of the otherwise-fine device dwindles. For the apps I've experienced this with, I don't even think they truly need the newer version of the OS. I imagine the developers just wanted to reduce testing and customer support overhead in most cases. For any app functionality that may actually require a newer OS version, I'd probably be just fine if that functionality were disabled/unavailable on older devices, especially if it let me use the rest of the app.