Dear Gregg et al.: 

From a scientific perspective, the JH actually helps answer the very question you're posing!  Plus, it's hard to claim an "original, new" theory if one ends up citing the work of someone else that has framed a similar argument for the past 15 years. The list here has enough experts, though, to comment on the psychological mechanisms at play. I'll comment on the sociological mechanism, i.e., the distinct nature of "status." The challenges of securing and maintaining status, especially in the context of scientific discovery (or any promotion of ideas) is fraught with danger, since status is essentially a zero-sum resource (I gain status at your expense - most dramatically if one thinks about the unique status one has in a monogamous relationship with one's partner, which also explains why "cheating" is especially egregious). I've attached a paper from last year where I outline a general theory of lethal punishment, which outlines the core logic of the importance of status and links that to the logic to the structural foundations of human interactions. 

On the more practical side of your question, Gregg, you'll note that I cite extensively the two original authors of the two main theoretical arguments I'm making:  Milner and Black. I was always taught that that's an integral part of what we do as scholars. Plus, I've always felt that citing others' work actually enhances the credibility of what I'm arguing in showing a certain continuity of thinking within a broader community. Of course, I have no illusions about winning a Nobel prize or authoring a best-seller that will make me famous! But the bottom line is that it's intellectually dishonest not to credit ideas as appropriate, especially if known. Curiously, did Hugo ever get back to you? 

Footnote: status (or reputation) = incredibly fragile. A breach in the form of plagiarizing ideas or not acknowledging those who have expressed them previously is one of the "cardinal sins" that actually destroys reputations. Look at how severely we police plagiarism among our students. At my institution, anyone caught has to walk around on campus in perpetuity with a scarlet "P" (for Prynne?) on their clothing...

Best, -Joe