Although, to be fair, in this case I agree that it's not an appropriate question for an interview, Why? As an interviewer, I think it tells me a great deal.

Although, to be fair, in this case I agree that it's not an appropriate question for an interview, Why? As an interviewer, I think it tells me a great deal. It certainly should not be the focus of the interview, but I want to know things like: 1. Will this candidate mesh well with the existing team? 2. Is this candidate going to take the initiative to learn useful things on their own? It seems to speak quite well to those issues.