There is a point for the king it just is rarely mentioned. It's infinity. If you lose the king you lose the game and therefore it is infinitely more valuable than any other piece. Most people use points to help to evalute whether an exchange is good or to work out who has more material.
Of course, there is another sense in which pieces have points which is their value as a defender or an attacker. In this sense it is probably worth 3 or 4 points. There was a previous discussion about this. See http://www.chess.com/forum/view/general/how-much-is-a-king-worth
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why there is no points for kings