They missed the RAND editor.[1] This was a full-screen editor of the late 1970s, years before "vi". It was originally designed for a specific HP terminal [2], one which had programmable function keys, and there was a little plastic overlay to place around the function keys indicating what they did. Later, there was a custom terminal with built-in keys for the editor functions. Expecting users to remember control sequences was considered unacceptable.
The RAND editor wasn't free. We had a site license for it at an aerospace company, so it was on all the UNIX systems. It was not used widely outside aerospace and DoD. "vi" was an attempt to do roughly the same job without the special hardware.
Maybe they felt there was no known or documented relationship between that editor and vi. Then again, they missed Bravo (which ran on the Alto) and Bill Joy has talked about its influence specifically.
Bravo is completely different. It's mouse-oriented, with proportional spacing and multiple fonts. It's the ancestor of Microsoft Word. Charles Simonyi worked on both Bravo and Word.
You can use Bravo as a programmer's editor, because the file format is plain ASCII followed by a control-Z, then formatting information. Alto compilers read the plain text part and stop at control-Z.
The RAND editor wasn't free. We had a site license for it at an aerospace company, so it was on all the UNIX systems. It was not used widely outside aerospace and DoD. "vi" was an attempt to do roughly the same job without the special hardware.
[1] http://www.rand.org/pubs/notes/N2239-1.html [2] http://terminals-wiki.org/wiki/index.php/HP_2645A