I am going to have to agree with you on this one, and I am in the generation who seeks online gratification from everyone. I don't see the point in adding an interviewer on LinkedIn. You're not friends, you're not colleagues, in fact, the only reason you're aware of the others existence is through the compulsion of the hiring process in introducing you.
I think it's fine to ask to connect on LinkedIn with someone who interviews you after they offer you a job, OR after they inform you that they are not going to hire you. If you connected well in the interview, got good feedback but just didn't quite make the cut, I think it's fine to try to connect with them then. They are now a potential networking contact for you. I just wouldn't do it in the time period between seeing their posting and hearing their final answer as it might be awkward for some people at that point.