Well, Kokoa had her fill of Tsukune also, whos to say Akuha or Kahlua wouldn't?, they will probably get their "turn" in the future.
Though i do agree, Moka will have her objections.
Besides, if i was Tsukune, i wouldn't mind being in the "middle" of it all.
Having a vampire drink your blood, i mean, how awesome is that.