For two years now my greatest complaint about studying ancient history is a spotlight effect. This effect is that in the primary sources certain “great” men dominate the attention and it is impossible to know what else goes on. The best example of this is Alexander III who has at least three ancient works dedicated to him and another that covers him extensively, yet it is nigh impossible to know what some of his officers, in particular the more junior ones, are doing at a given time. Alexander has a spotlight on him that follows wherever he goes and we mostly know what the other men were doing as they entered the spotlight.
Of course there are other problems with the histories, not least of which is that their source was mostly Ptolemy who in turn rewrote history to slander his opponents and make himself show up more often, but Alexander also hogs the spotlight. Some of the time what Alexander ordered and the sparse information from elsewhere does provide adequate knowledge, but other times men who are not immediately around him disappear entirely.
With Alexander I can somewhat understand it because in terms of pure charisma he was by far the most dynamic person of his time, but it is a disservice to the men who served under him who were often brilliant military commanders (Parmenion likely had a better grasp of strategy, if not tactics than did Alexander, Krateros and Seleukos were each defeated but once, etc), fiery personalities (Krateros and Hephaestion fought each other at one point and only Alexander stepping in prevented a battle), and so on.
Still, this is a recurring trend in ancient scholarship, and really before there was information commonly available for what pretty much everyone did, and is one of the difficulties of scholarship at such a great length.