Because Yuko didn't have a PV for it I think... ahah, and not to mention Kusumi had one to.
Hehe Kusumi's was horrible but it deserves to be mentioned.. Yuko's was extremely slow but I liked that, I would have voted for Yuko if on the poll.
Edit: Voted for Mari, surprised that I was the first.. Dunno something about it being in a classroom, reminiscing the past I liked that.