The constitution of America was put into place during a time that we were incredibly bitter towards Great Britain and what we perceived as unfair ruling from a less than satisfactory king. We have been allies with our mother country for a time, and many of our ideas have changed since 1787. We should not be held accountable for the decisions of our forefathers, and although they put an incredible amount of effort into the constitution it's almost impossible to account for everything that might happen in a countries future. Some examples of this in action is the conflict between jefferson and the Louisiana purchase during his presidency, or the civil war. If we remade our Constitution with future generations in mind we may be able to minimize misunderstandings from the public and politicians regarding outdated morals.
The people of the United States went through a great time during the Revolution, and those present know what corrupted the people. With the struggle that occurred then, how are we to insure that the changing would not cause disputes among the people. The Constitution is there to lay out structure among the people and in the case of the Constitution being remade what would happen to the old things included in the Constitution when it is being rewritten, not to include the chaos which would happen when things change among the people and in the government.
The Constitution was created for the foundation of our country, it's worked for 240 years to help run our federal law system and lay down our basic rights. What if they remove the right against cruel and unusual punishment because it was from another time? We'd have criminals being treated inhumanely just because it's a "dated" rule.
The purpose of the Constitution was to lay out man's basic, unalienable rights. The founding fathers of America wrote only the most basic things so that even in the future, men would be treated as men should be.
Allowing whatever officials happen to be in office word a new Constitution to their benefit, just like they do laws, would be devastating.
America is built on our current Constitution. If you don't like it, leave.