PCs didn’t have as long of life in the 90’s to the early 2000’s, either. In 2008 only 33% of PCs were over 3 years old. Today it’s over 60% (haven’t found a more exact statistic). iPads were going through a similar maturing process and rapidly iterating on performance and features. It’s why I can accept the notion of hardware being obsolete sooner when being an early adopter.

The big thing that makes really old iPads not worthwhile to reuse is the battery. It often becomes cost ineffective to replace them. I’m looking at my 9.7” Pro with a cracked corner of its screen. Replacing the battery will damage the screen more causing a replacement for that, too. PCs don’t have the same expectation of parts wearing out - many easily can run 10 years with no hardware maintenance.