MCW fills up their class pretty early. They don't send the invites for the waitlist until February, I believe. I think their thought process is that they would like to interview applicants who are really interested in their school at that point. Someone with an acceptance may go to a regular interview to compare, but is probably more unlikely to interview for a waitlist spot.
(this of course is my unprofessional opinion, as I don't know much about MCW - I was put on a pre-interview hold!)