Because the race for the presidency is about electing the executive leader of the United States, a very serious and important role. It is not about a freak show.
From the comments I've seen here following the recent Bush/Kerry "debates," I would have to disagree with you, RW. Kerry has been called everything but human.
If you can, put yourself in the shoes of the estimated one-third of the voting-age population which aligns itself with neither of the dominant political parties. Then ask yourself, why am I asked to choose between the candidate from Socialist Party A and Socialist Party B, whose disagreement on the most trivial matters would, to an outsider, seem almost contrived.
As a political junkie, you no doubt are familiar with what the Libertarian Party stands for, are you not? And the Constitution Party, also? And the Reformers, if they have a platform left after the 2000 fiasco?
Don't you think the vast unwashed who read only the sports page and maybe the horoscope column in the daily papers are entitled to know that there are valid points of view other than that enunciated by spokesmen for the dominant socialist/fascist parties?