Because if you think about it, if say you had had everyone's third choice vote, you would have ended up with a score of 0, even though everybody voted for you. Reason being that you would have gotten knocked out after the second round.
Which is before the third choices start figuring into the calculations.
No - you are slightly missing the point. In this election, sure I would have been knocked out then, because Paul was sooooo far ahead of everyone else. The ones who get knocked out are those who cannot get enough votes to win the next round