I might be projecting, but having hung out with Carter (the author) a few times while he spent this past summer out here in Palo Alto, I can probably assure you that it's just an un-stated assumption that's causing you guys to differ. The reason he's asking that question of "what value do you add?" is because it leads to personal fulfillment. Some people are personally fulfilled by shaving basis points. Hell, I could be one of them if not for the the lost forests of entry-level finance work.

Carter is talking to people that want to have huge impact on society. They dream to be Rockefellers, Jobs's, Brins, and so on. In those cases, it's always worth stepping back and thinking about what overall impact you're having. If all you're doing is shaving basis points you're probably not changing the nature of society.

And no, this doesn't rule out finance; J.P. Morgan diverted the vast holdings of Europe into the burgeoning economy of these United States (http://en.wikipedia.org/wiki/J._P._Morgan#Treasury_gold) during a crisis.