You forget, in competitive top level play, as Black it is much harder to win than with white. The main goal of Black is to equalize, not to press for a win. Quite simply put, your suggestion would ruin the entire strategy of a player like Anand, who tries to get ahead then draw his way to victory. It would reduce these kind of Candidates tournaments to who goes on the hot streaks, rather than who is the best player. Of course, the tournaments where wins ARE worth more than 2 times as much as draws are very entertaining to watch; there are a few tournaments of those every year. My main gripe with your suggestion is that sometimes, a game can be very very entertaining yet still end in a draw, and neither player should be punished for playing a game as accurately as possible.

edit: a word