Cite your sources and give them credit–it’s easier said than done.
On one hand, it’s easy to encounter philosophy papers that fail to cite enough sources. It’s easier to cite the usual suspects that others already cite than to exercise independent judgment about who deserves to be cited. In my experience, philosophers’ citations go disproportionately to authors, preferably male, who work in “top” departments, publish in “top” venues, or are already cited by other “star” philosophers, or to authors who have achieved “star” status. It would be great if we all did our part to correct that bias at least a little bit.
On the other hand, there are way too many publications for anyone to attempt to research everything that could be relevant to one’s work, or even a large proportion of relevant sources, to determine whether they should be cited. If you try to cite every source that could be relevant to your paper, let alone book, you’ll hardly ever get done.
As is often the case, we should strive for a reasonable middle ground. Do your research, use your own judgment, and make it a point to cite at least some people who did valuable work even though they are not highly visible in the profession (yet).
Citation fairness is especially important for those who write review articles, such as SEP entry. I recently witnessed an episode where a revised SEP entry omitted a highly relevant paper. When the omission was pointed out to the SEP author, they responded that they intentionally omitted that source because it was not yet “influential or widely cited”. I realize that it’s impossible for you to assess this situation without knowing the specifics of the case. Suffice it to say that, in my own judgment, this SEP author did the opposite of what they should have done. They are the expert: even though they can’t cite every relevant source because there are just too many, it’s their job to cite valuable new work so that others know to cite it in the future. That’s what I try to do in my own SEP entry (co-authored with Corey Maley).