The thing with Vista was it was it was th3 first really major rebuild of Windows in a long time. Going to 98, ME, XP, etc you had increased minimum specs, but things like drivers and shit generally worked fine, so as long as you had the necessary RAM and processor to run the OS, you could just install the new version and shit would probably work.

So when Vista came along, the manufacturers selling existing models just shipped with the new OS expecting everything to work without testing.