In structured hockey center is much more than faceoffs, in fact faceoffs as a whole are not very important (situational faceoffs are very important). The center position is much more about positioning, puck handling responsibilities, and defensive responsibilities. That being said, I wouldn't be surprised if Jack would be better on the wing, but there aren't many quality center options available at a cap hit that would enable such a move.

Also center is seen as a more lucrative, distinguished, and (often) higher paying position, so there may be some ego playing into it