The reason the productivity of CLIs was often extolled is because throughout most of interactive computing's lifetime, CLIs and scripting have been intertwined.

The reason the productivity of CLIs was often extolled is because throughout most of interactive computing's lifetime, CLIs and scripting have been intertwined. It was possible and commonplace to invoke parameter-oriented CLIs from another process, and use the CLI as a perfectly adequate API, while other interface paradigms like TUIs and GUIs never quite achieved such ease of programmatic manipulation.