Before the term "intuitive" was bent a little by common usage in the tech fields, it had a basis in "unconscious competence." Unconscious competencies based on in-built the physical modeling tools of our nervous system are very powerful. Leveraging these in-built capabilities to build our UIs is also very powerful.

Awareness of all of these different sorts of "intuitiveness" probably distinguishes the excellent UI designers from the average ones.

EDIT: Not only are the unconscious competencies very powerful, they also tend to be highly optimized.