Two key reasons (others have been mentioned): the output is purely digital, and incredibly abstract. Code is very unique in this regard. As a purely digital ar

Two key reasons (others have been mentioned): the output is purely digital, and incredibly abstract. Code is very unique in this regard. As a purely digital artifact, it is highly malleable. Yet its deeply abstract nature, and the complexity enabled by those abstractions, make software very difficult to inspect and understand, compared with the vast majority of things humans make.