Because USC is ambiguous, so the votes get split. Sorry for the flippant answer, but is this a real question anyway? I know that OSU has a built in advantage by being OSU, but this year puts a fine point on how completely ratings-based these football rankings are. 6-0 Ohio State has a monumental advantage over 6-0 USC because reasons. They've also made it clear that a Group of Five team will NEVER make the playoff, as they keep dropping undefeated Cincinnati below one or two loss teams Clearly you haven’t watched USC play if you think they’re worthy of going to the playoff.