Nice refresher. Under purposes, numbers 1-5, and half of 7, all, for me, are subsumed under the objective of providing new information or insight (the other half of 7, persuading an audience to accept an old conclusion, doesn't carry far with me unless it has one of the other numbers going for it!), and number 8 hopefully has the virtue of some compelling, humerous, or other positive style going for it.
Number 6 leaves me cold, unless there are other of the numbered purposes present (perhaps in greater measure), for if it is old info be represented, one wonders how the new presentation is better than the old (simply availability or affordability)?
Among audiences, I presume numbers 1 and 2 are dead losses for a commercial publication. Number 3 must be risky, and number 4, and to an even greater extent, 5, are where the money must be. But even when writing for the latter numbers, presumably some of the virtues of a product aimed at the earlier numbers might be imported in the hopes of helping raise standards of consumption and production...a rising tide lifts all boats, sort of thing...?
And I heartily agree with your point about wargamers, who can sometimes occupy a sort of amateur niche that seeks to grapple with nuts and bolts issues that otherwise can pass unpondered.
Thanks again for the refresher. Always nice to tighten up the thinking!
Appreciatively - Howie