I really doubt an average Joe would buy a new computer once the old OS goes end-of-life. Joe would just continue using an EOL system and hope everything is alright.
Having worked in tech fields, legacy devices as old as 20 years can pop up occasionally, functioning or not. Once was told a story where this tech was hired to fix a highschool bell system and the whole thing was running on windows 98. This took place in 2015 or so
The restaurant I work at still uses Windows XP on one of its main tills. It breaks down and freezes constantly.
I work in a field that is considered by many high tech. I have personally seen a system in use today that duel boots windows 2000 and windows 98.
The product it’s used by is old generations and the system does not have any network access but still must be supported by government regulation for several more years…
Few years ago there was a story in a local paper about building automation systems running on Commadore 64 and still doing fine. Build by some company in the 80’s. They weren’t online, so no security issues.
Tried to find the article online but no luck. It would have been in local language anyway.
Even if they was online, I doubt a lot of people have the knowledge for hack a commodore 64.