When you use a computer these days mostly it is quite straightforward, at least for familiar everyday programs. When you try a new application again it is pretty familiar. If you have to consult a manual it is either because you’re trying something very unusual, or because the user interface to the program is not too good. Manuals are often incomprehensible, and anyway these days we don’t have much time to consult them. We expect everything to just ‘work’ and be easy to understand.