And as for Windows updates we don’t know what the future holds. Windows Vista and 8 certainly wasn’t supported for decades.
Linux distros are fine as long as you do dist-upgrades, but that’s not something most people’s grandparents, heck, even most people, are going to do even if they were able to walk into a store and actually buy a computer with Linux on it.
And as for the edge case Macs which only received four years of software updates - I’d be pissed if I was the owner of one.