Desktops can take a long time to become obsolete nowadays
I have an 8 core AMD mini tower running Windows 7 with SSD (upgraded at some point from spinning rust) and 16GB RAM. It was new when Windows 7 was pretty new and cost significantly less than half the price of a typical Apple PC at the time.
It is still used daily, still outperforms many laptops and still works great for multimedia, including 4k video (which is mainly what it is used for).
If Windows 7 becomes problematic, due to end of life, I can put Linux on it and it will even appear to run faster!
It would get hot if it wasn't water cooled, so the only reason to 'upgrade' to something newer is to reduce my electricity bill, but this is marginal compared to the cost of upgrading.
Gone are the days when CPU clock speed on the latest PCs appeared to double annually. We haven't even seen much improvement in the number of CPU cores or RAM on average hardware in the past 10 years.
So it's no wonder that PC sales have fallen, whatever form factor, because we haven't really seen any useful performance improvement in the past 10 years on the average PC. 10 years ago Libre Office or MS office and most other commonly used software ran just as well as they do now on the latest kit at that time, so why would anyone buy new kit???
Of course Microsoft bloats Windows to make it appear that we need new hardware and therefore pay more Microsoft tax, but it's amazing how fast quite a lot of older hardware is after migration to Linux.