Thing is, we now have 10 year old computers that can stiill run basic tasks just fine. With SSDs, longevity has been extended as well. Of course, Apple has a second agenda. I'm sure Apple wants to drop all intel macs from support ASAP so they can ditch the x86 code and focus on their own silicon.Apple has gotten better about this over time. The latest Mac OS supports my 2015 MBP and the 2015 MBA. That's 7 years, not bad, and the next version may even keep support. Generally they also provide security updates 1-2 versions back, so on a 2013 Mac, you're probably fine running Big Sur.
It's not just Apple. Even Microsoft does it with Windows 11, dropping support off anything older than intel 8th gen CPUs, dropping machines as recent as 2017/18. And Windows 12 is coming in 2024, and I have a feeling that Microsoft is going to be Apple-like, dropping support off CPUs every few years. So much for Windows 10 being the "last version of Windows."