> Trying not to beat a dead horse, but I recognize there may be many reasons people come up with for writing a new library instead of reusing one. My point is t

> Trying not to beat a dead horse, but I recognize there may be many reasons people come up with for writing a new library instead of reusing one. My point is that it has a business impact to do it that way, because unless that library is open-sourced, the next time it happens it will be an overall loss for the industry due to solving the same problem again and again in slightly different ways. One of the reason to use Lisp was to leapfrog the competition. See for example: https://paulgraham.com/avg.html https://paulgraham.com/avg.html Applications were written in novel areas by small teams. The commercial Lisp vendors had their development environments bought and be used by these teams, but they could not post success stories, because they were not allowed to mention the customer and its application. Here often substantial and complex software had been written, at the core of some new business venture. The reason this software code could not be used by, then was not that it easy to copy, but that the developers did not want to give their competitive advantage away. For Lisp libraries -> if any library domain gets complex, there will be only a few ones which actually get used, because it was non-trivial to write. People might try to write simpler or new ones, but the better ones are hard to replicate and Lisp developers will tend to use those. For example the Lisp cookbook recommends one Regular Expression library: https://lispcookbook.github.io/cl-cookbook/regexp.html https://lispcookbook.github.io/cl-cookbook/regexp.html That's what most developer tend to use - it is widely ported, written in good style, well tested, ... A strange thing in the Common Lisp world is that new developers stumble of old libraries. They expect libraries with lots of bug fixes and a long maintenance log. But the library hasn't much touched in since some years. They detect then, that this library is "done". It has reached a state where not much needs to be done. This is also an effect of Common Lisp, where the language is mostly stable for several decades and code can be used for a long time without the need for a new attempt.