Mark - I did a quick search and found that several other Bible Software companies, including free ones, were still selling the 77 version alongside the 95 version. Some even had both bundled together.
Interesting. I don't know what could be done. Logos has stated it can no longer sell the '77 version, but we haven't been told why not if an effort were made whether that could change.
I would suggest a suggestion be made through the suggestion forum to this effect.
I have the '77 version in Logos but really use it infrequently. I have bound study Bible in the '77 NASB that I sometimes bring out. When I do it is handy to have the older version on Logos to follow along with. Handy, but not essential. I wonder if I'd buy it if it were available in Logos and I didn't already have it?
Here is the suggestion. There seems to be an interest in this.