As me and others have said all over this thing, Windows 10 no longer getting updates doesn't mean it's mandatory to update. Most of the users you describe will not notice or care that security updates die out and they will just take whatever runs in the next PC they buy, as they normally do.
This mostly matters to power users and corporations. If that. I'm arguably a power user and have zero intention to upgrade my legacy Win10 machines for this reason, either.