The complaint is more about bad interfaces. One of the examples (unix command line tools) has a very clumsy interface if you're trying to use it from within a

The complaint is more about bad interfaces. One of the examples (unix command line tools) has a very clumsy interface if you're trying to use it from within a lower level program: create pipes for input & output, fork, exec, use i/o on the pipes to feed data in and get results out, waitpid, figure out how the tool exited... this is slow, annoying to implement, has many failure modes that would not exist if the interface were a direct function call, and it's inflexible in that you'll be unable to use the core functionality provided by the tool if your data cannot be realized as a simple text stream that still makes sense to the receiving tool. And you can't extend the core functionality e.g. by passing another function to it. That's a huge amount of friction to using code that is already there, because of bad interface. And that's why people reimplement those tools instead of composing programs using those existing tools. Likewise, FFIs exist, but often it's just easier to reimplement something in your language instead of trying to use the existing implementation from another language.