Person reflects genre. Despite the fact that he is an eighteenth-century author like Sterne and Chesterfield, Franklin uses the first person more often because he is writing an autobiography, a literary kind that, except when it is an exercise in voluble self-concealment, like The Education of Henry Adams, depends helplessly upon the first person. Similarly, to accuse David Copperfield of “ego-involvement”—he uses some form of the first person 6.3% of the time—does not seem quite right. David is as much a “camera” as Christopher in The Berlin Stories; he is at least as interested in the people in his life as in himself.
Myers quotes David Cooperfield's first encounter with Uriah Heep, and notes
David refers to himself eleven times in this passage—exactly five percent of the words are first-person forms—while referring to Heep just seven times (ten, if the references to Heep’s eyes almost as impersonal objects are included). Yet his entire attention is on Heep, not himself. The narrative strategy is to register Heep’s effect, because that is how—at least for Dickens—a man is to be judged.
There's another possibility as well. One of Jamie Pennebaker's generalizations about the social-psychology literature on pronoun usage is that in conversation, "Usually, the higher status speaker will use fewer 'I' words." This is not, I suppose, because the lower-status speaker is registering the other's effect out loud. But perhaps in such situations, the higher-status person can afford to focus on the content of the discussion, while someone in a socially inferior role needs to worry more about the relationship and how they should or can fit into it. And this might be true even even of their interior conversation with themselves, as in the Dickens passage that Myers analyzes.
To learn more about these questions requires counting how pronouns are used, not just how many of which are where. For a classic non-pronominal example where looking at function leads to a different conclusion from simply looking at form, see "Gender and tags", 5/9/2004.
Unless first-person genres and their self-referential purposes are taken into account, complaints like Fish’s and Noonan’s about “self-reverence” and the “imperial possession” are empty moralizing.