> This is not a reasonable expectation.
I may be of a different age, but in my time it was common to buy computers without any OS pre-installed. It was on you to install one (from CD, floppy, whatever).
Of course, vendors selling PCs often also sold OS's...
This is still the case. You can absolutely buy computers without an OS, but most people don't want that so they aren't quite as easy to find.
Here is an HP without an OS: https://www.newegg.com/p/1VK-001E-4UPC7
If you want something that most other people don't want, it is going to be a little harder to find. That isn't a conspiracy, that is just life.
Sorry but this isn't the 70s. Even businesses expect devices to somewhat work out of the box so it's completely unreasonable to everyone except people who buy things like Raspberry PI, which are a tiny minority.
Expectations change over time.
But I also believe your recollection is erroneous or must differ by region because I was there as early as the 80s and computers sold without an operating system weren't common. If you were buying a PC clone in the 90s you could buy it without the Windows license, of course, but the default was to include it.
Even before PCs, computers typically shipped with BASIC, which was their operating system of sort. Macs, Amigas, they all shipped with an OS as well.