[wizzwizz4]

There's very little NT 3.1 code left in Windows, but it's still clear how old that project is.

[trustno2]

All unixes are descendants of original Unix from PDP-7 days. Why does it matter?

...ok the /bin /usr/bin nonsense still stays after decades, maybe you have a point

[mattl]

Windows, macOS and Linux all have legacies of the late 80s and early 90s.