[EGreg]

Here is the main reason:

Any sufficiently advanced software has deep structure and implementation. It isn’t like a poet who can just bullshit some rhymes and make others figure out what they mean.

The computer program expects some definite inputs which it exposes as an API eg a headless CMS via HTTP.

Similar with an organization that can provide this or that servicd or experience.

Therefore given this rigidity, the input has limited options at every step. And a GUI can gracefully model those limitations. A natural language model will make you think there is a lot of choice but really it will boil down to a 2018-era chatbot that gives you menus at every step and asks whether you want A, B or C.