Dennis Kucinich and Ron Paul are certainly the most interesting and provocative candidates running for president. I love that Kucinich wants to set up a Department of Peace and that Paul wants us to stop acting like an empire. They have no chance of winning, though, and for good reason. Liberals are more sensitive to market failures and more willing to step in where businesses fail. Conservatives, by contrast, are more sensitive to government failures and are more willing to stop subsidizing failed government programs. But some liberals simply go too far and just don't trust markets, ever. Same goes for some conservatives and government programs.
It's not true that Ron Paul wants to abolish all government or that Dennis Kucinich wants to abolish all businesses. But they both stray close enough to such positions to have earned Americans skepticism and distrust. Kucinich's health plan isn't just an attempt to step in to rectify market failures. He makes explicit his distrust of markets when he says that companies ought not to profit off of illness. It would be hard to pack more misunderstanding about capitalism into a single sentence. Ron Paul basically wants to do away with all government programs save defense. (Okay, so I'm exaggerating, but not by much.) He wants to keep us from the pitiful lifestyle of the Swedes (where the tax burden is over 50%) and imitate instead the enviable lifestyle of the Mexicans (who suffer a tax burden of only 18.5%).
The reason that Paul and Kucinich have never gained much traction in the polls is that the average American - however much he's become disgusted with businesses or government - still fundamentally believes in markets and elections and the results they produce. Most of us have caveats about such beliefs, but very, very few Americans believe in doing away with government programs or company profits. For that reason, the two men who carry suspicion of these two institutions the furthest have found themselves the furthest from the center of the American polity and of any hope for victory. For Americans, disgust with government programs and profitable companies is like disgust with family; it's inevitable but not to be construed to mean they're ready to be estranged. For all their kvetching, Americans love their markets and elections and are not only willing to live with the results but are unwilling to live without them.