The thing is, if you were a user of multiple different UNIX systems the previous century, it was much the same - vi was the only editor installed out of the box

The thing is, if you were a user of multiple different UNIX systems the previous century, it was much the same - vi was the only editor installed out of the box on all of Solaris, BSD, Tru64, AIX, HP-UX, Linux etc. So if you were frequently moving between them as some of us were, you wouldn't get very far if you didn't know at least the basics of vi.