Because even though 67% of Americans favor using diplomacy when dealing with America's enemies, and 59% support talks with Iran, Congress is fast tracking a resolution forcing a blockade against Iran. They can't sign it fast enough. Forgetting that our own NIE from last year has stated that Iran gave up it's nuclear ambitions five years ago, I guess Congress thinks they know better. And remember, these are the same people who voted for war with Iraq, despite there being evidence that the Bush administration was lying.
And therein is the problem. Once you get mired in a place like Iraq, it's hard to pull out. Right now, despite Scott McClellan's new book stating the Bush administration used propaganda to turn public opinion in their favor, no one has suggested that maybe since there are no obtainable goals, maybe we should get the fuck out of Iraq. John McCain thinks that Iraq isn't important, but then why does he think we should stay there a hundred years?