>>3664863Because they are there to interact with Shinji and it's through how he does that and how he acts around them that you get to understand how his mind works.
Why does Shinji feel at ease with Kaworu and not with Asuka? Why is Asuka an object to Shinji but Kaworu is a human just like him? Why can't Shinji put himself in the place of Asuka, but can understand in the end what Kaworu is?
Why is Kaworu love and communication but Asuka hatred and confusion?
Both Asuka and Kaworu do have characters of their own just like everyone else but EoE focuses on all of this through Shinji's eyes. That's why characters like Misato, Rei and Kaworu are not "saved" at the end, unlike what happens in Rebuild
