There are a couple, first an old work box is only 'Approved' for you guessed it 'Old Work' NOT new work. Inspectors can be particular about approved devices.. Second all the wiring needs to be inspected fully before the wall covering goes up. Boxes installed, romex run, stapled wires sheath stripped inside of the boxes and all grounds 'bonded' together with a mechanical device (not a wire nut). This is so the inspector can fully inspect everything that will not be visible after the wall covering goes up. By bypassing this, one could attempt to avoid inspection of most of the wiring.
Also, the next inspection (and final) would be with the covers on the boxes so they would never get to see the inside of the box including the stripped wires and ground bonds.