And if you have open source drivers that continue working and the upgrades are free, what possible reason do you have for not upgrading?
The userland ABI and APIs are stable and have been for a long time, code written for unix systems of the 80s will still compile and run just fine on a modern linux system.
Windows users stick with the version they got because upgrades are expensive, often cause performance degradation or require a troublesome clean reinstall, and may break compatibility with existing hardware or software.
The only time problems like that occur on linux is with closed source software, none of which i use... I regularly upgrade my linux boxes for free to get new features or other improvements, and the upgrades are gradual so you can get used to changes rather than a hard slap in the face every 5 years or so.
I continue using my "obsolete hardware" because it still works and still serves my needs, I could buy a new replacement but it would cost money and wouldn't serve my needs any better. Your argument against using obsolete hardware also applies to obsolete software, windows users keep using the version they got with the hardware because any benefits are outweighed by the negatives of upgrading.