People would need to passionately dislike the potential winner to want to vote anyone else as an alternative.
Taking a look at the final 6, they are all dreadful in my opinion, all pretty horrible people in 1 or more respects. Put trash in and you get trash out, there really isn't any escaping that.
What does winning CBB actually mean? Absolutely nothing, there is no winners cheque, no winners show, no winners record deal. Its a pointless and worthless title. The civilian series at least has some cash associated with winning, so there is some reason to it. But, with 6 people left, and no point in voting .... why bother ...