One word Politics, there isn't a political consensus for this type of sweeping tax reform, politically it would be suicide for conservatives to allow for the creation of a NRST without the repeal of the 16th amendment, experience show we would end up with both types of taxes. Aside from the current tax reform (WHICH DOES ESTABLISH THE IDEA THAT DOUBLE TAXATION OF BUSINESS PROFITS IS WRONG, a key idea in a Flat Tax plan), I think Medicare reform is the big idea for this election cycle (which is scary lots to go wrong here. The other biggies are judicial appointments and a PBA Ban (the most important thing to be accomplished this session of congress).