Let me get technical here because this was part of my job (at another kind of industry) when I was a 9 to 5 guy.
The industry in the early/late 90's was in it's infancy when we consider game development. Ok I get that Nintendo, Sony, Sega (Sega not that much, Sega was always a mess from what with saw afterwards on the hardware front) were very structured companies on the hardware front but on gaming development?
Data/Documentation management in project management and documenting "lessons learned" only became a sepatate discipline in project management in the early 2000 and only became a recognized "real" important thing in the 2010.
And here I'm taking about very structured business companies, not some 90's gun-ho 30 guys, like most of the big game development companies were at the time.
It's not their fault per se. They were just getting bigger and structured at the time + the difficulty and cost of cataloging, archiving and store this type of content at the time.