The problem with throwing out the Constitution and starting over (which is something that even Thomas Jefferson advocated for every generation) is that in this political climate, a lot of good things would be thrown out and bad things enshrined. You think Freedom of Religion would stay in the Constitution unchanged when the Tea Party insists that Muslim Americans and atheists don't deserve the same rights? How about press freedom? How about second amendment, which needs modifying; do you think politicians will make it easier to get a gun or harder? For that reason, it's very hard to change without opening a Pandora's Box of politician tampering.