Your raw numbers put you in the running, but it was unwise to not take the interview. Even when a school says the interview is only informative, they are ALWAYS evaluative. At my interview for NU, my interviewer told me directly that we would write me a great recommendation (we really clicked). Not only do alums evaluate you, but simply taking one allows you to display your interest in the school.
Let me put it this way - my mother is an alumna as we visit NU a few times a year. I took an interview, not wanting to learn anything (because I almost literally know everything about NU), but because I wanted to display clear and enthusiastic interest in attending NU.