Lisp machines were mostly just a single type of computer: a graphical workstation for Lisp developers. Those were mostly in R&D, typically in AI - largely finan

Lisp machines were mostly just a single type of computer: a graphical workstation for Lisp developers. Those were mostly in R&D, typically in AI - largely financed by DARPA and similar, hoping for the AI software providing leadership in tech and military. The market for their software&hardware was on the leading edge, which later was taken from offerings growing on cheaper platforms. They had one/two operating system to fork others from: single user, no terminal story, no security, needing large amounts of memory, needing specific expensive hardware (graphics, disks, custom boards, ...), not easy to port, needed complex (and hard to debug) memory management, scarce number of Lisp system programmers accumulated in a small number of companies, no public source story, ... Many open source operating systems are copies or forks. There was not much original research. Writing a new operating system (say, a portable Lisp OS with device drivers, multi-user capabilities, security, terminal and GUI usage) would have needed a lot of work and there are not enough combined Lisp AND systems programmers to do that - educating them takes a lot of money. Even today, the state of the 70s/80s Lisp OS hasn't been reached again: there is no comparable operating system written in Lisp and the old ones exist only as emulators of the past. The tech base of the early Lisp system was too focused, there was no room to mutate and grow to different platforms in different incarnations. There were attempts (like embedded Lisp hard- & software) but that had no effect in the market. UNIX was developed for a completely different market: simpler base software, very portable, multi-user, client&server, modular programs, terminal, ... a bunch of companies used UNIX as a base for their workstation offerings (SUN, SGI, HP, IBM, NeXT, ...) - the rest is history. But Lisp OS like software on the UNIX systems was working well in the 80s and early 90s. They still needed large amount of RAM, large amount of virtual memory, responsive GUIs, advanced GC support, ... some high-end machines could offer that and they fixed enough OS bugs to run large Lisp systems. Every larger UNIX vendor had some Lisp story as part of their general offerings.