CUI command parsers are often big and ugly to write. Programs having CUIs are hard to combine with other programs. CUIs do not scale well. CUIs do not take advantage of software leverage. Make every program a filter.
Every program written since the dawn of computing is a filter.
Computers convert data from one form to another. Ten Lesser Tenets Allow the User to tailor the environment. Make operating system kernels small and lightweight. Use lower case and keep it short. Silence is golden.