It does indeed. But remember one of the big sells Microsoft made was that with Windows 10 you would get continual security patches. Microsoft dug that hole for themselves.

And to add, a machine released in 2015 (less than 3 years ago!) that no longer gets security updates is hardly the right place to be drawing the line you speak of.

No. But manufacturers ought to warn their customers that they don't intend to support their hardware for longer that some period of time so that people can at least buy their crap based on an informed decision. It used to be that you could run Windows until it EOL'd giving you a good couple of years, now with point releases you are only guaranteed to run it until it reaches EOL of that point release.