Never having written anything for public consupmtion beyond magazine articles, and having neither the time nor inclination to write a book, I hesitate to offer my twopenneth.
It seem to me that the motivational factors you mention tend towards the altruistic, and ignore the satisfaction the writers get from their activity and the possibility of reward, be it either peer recognition or money.
Points taken. The motivational factors mentioned are largely altruistic. That is the definition of any professional set of ethical and technical behaviors--a striving for excellence apart from monetary gain. To strive for excellence is alturistic in many ways, but it is also a major source of writer satisfaction. It certainly doesn't guarantee any kind of reward in this world, even peer recognition.
I concede that most writers of history have 'day jobs', but their are a few for whom history is their exclusive profession.
John: Now that can mean that they can't be expected to act in a professional manner or pay attention to historiography, or that can be one reason why they can afford to be altruistic. :-j
I do agree with you entirely that the target audience is fundamental, and this applies to the dissemination of anything really. In my profession one often has to write several versions of a single document. For the professional and specialist it will often run to the size of a small book, together with supporting evidence, but for the most senior lay readers the same document will be distilled into a couple of pages.
Yes. Knowing who is reading the history, knowing the information they will want and find irrelevant is a real art, but necessary. Your work obviously gives you quite an insight into that.