Secondly, many Help files use words without explaining their meaning, and learning stops as soon as the learner doesn't understand one word. An Internet news-reader I used explains how to subscribe to a newsgroup, without explaining what was meant by the word subscribe, in fact in never explained what a newsgroup was. This is inappropriate since the action or item referred to might not related to something in the learners' previous experience. Without this reference it is much more difficult to understand. Thirdly, as a consequence of this lack of explanation there can also be gaps in one or more of the models, maybe the learner has seen something but doesn't have a name for it, or knows a word without knowing the object it refers to.
Understanding is much less likely to occur if the models mismatch.
Fourth - many Help files seem structured in the same way as the menu structure of the program. This is not how someone learns to use a program. As an analogy consider learning to drive a car, few people master the steering wheel completely before learning the gear shift. Most would gain a basic competence with steering, gears, brakes and navigating and then move on to learn the finer points. In a mail program you might want to know how to change the network connection settings.