Something about just not feeling that way, I don't know exactly what.
I do know if you run with Tekehu and Eder eventually banter takes them to have Teke saying "you and the captain traveled together all this time and you never?" and Eder replying with "That's not. uh. Not how things played out. Just never saw it that way."
So it does make sense in the way that Eder just never saw the Watcher with any feelings like that, he respected them but nothing more really. He does a list of everything but "feelings" that he saw them as but I can't remember it all. I'm disappointed as he would have been the only one I was interested in and it killed a lot of the excitement for me when he wasn't available but I understand it, they chose not to do as fans wanted for this character at least and made it this way instead.
When Ydwin died during combat next to a luminous Adra stone in my story she stayed dead. lol , i know gameplay vs story but still xD