Windows and Apple Operating Systems (OS) regularly update their systems. This is driven by the need to hire and employ software engineers. Okay, that is not true.
However, OS updates do appear mainly to drive new PCs / MACs or software package sales. This is infuriating. (I will stipulate that after a new release, they often make subsequent releases to fix things they were too stupid to find in the testing. Having worked with testers, I know this is usually lazy testing or a choice of things they don't fix.)
Apple and Microsoft add new features that either a small % of their customers requested or just something they brainstormed that would be cool. That would be okay, but these take up space and need more computing power, so they don't run on older machines. In particular, Apple benefits from this since they sell the computers you need, and then ends support for older models.
Most of the upgrades aren't worth the trade-offs, but both Windows and Apple make it difficult to stop the automatic portion of it. And, if you do, Apple stops supporting old OS version PDQ.
More than once (like 7 times in three years), the PC I used to show the training on for Project Management classes just crapped out and started an upgrade in the middle of my presentation. Since I only used it for training, I didn't upgrade it in a "timely" manner. I had to boot it up the night before to ensure it wouldn't upgrade. That still didn't always work.
We know upgrades aren't always needed, as seen with Southwest Airlines in the last crash that affected everyone else; Southwest was fine because it ran on Windows 3.1. Our ATMs ran on Windows NT (from the 90s) for over a decade. Maybe they still do, I don't know. I know the swap from Windows 3.1 to Windows NT required new hardware in every ATM. (A project management nightmare for yours turely, FYI.)
When Microsoft stopped supporting the release, we could still purchase support from Windows. And MAYBE these releases were safe from cyber-attacks because it wasn't worth it to hack for so few machines, but I don't know.
Without giving too much away, I know a young lady in Florida who is still running very old Microsoft, and she isn't having issues.
It is a sucker's game.