Power
This has NOTHING to do with security, and everything with increasing the power of the executive branch.
The political science concept of "cozy triangles" (sometimes called "iron triangles") helps explain how/why it's important. Cozy triangles provide a way of looking at the relationship between the purse strings (congress), the leverage position (the burecracy), and the eventual goal of any politician (provide "service" to your constituents). The more onerous and invasive the burecracy, the better it is for the politicians which weild control over it because it increases the importance of cutting through it for their constituents (something only they can do). The more "home service" and the less real policy making (and position taking) a politico can do, the better it is for them. Burecracies that politicians exert influence over are the problem they create in order to have a problem they can actually solve, and Mr. Bush wants that advantage for himself (and not congress). Public policy is hard, getting Fred Smith's medicaid check straightened out is much easier and is much less likely to make you enemies. Guess which one the pol will pick given the choice?
As is becomming the norm: brilliant political maneuvering on the part of the White House ("I help win a seat in november, you help me dissmember your power base") thinly veiled as "security". GWB may be as dumb as a turnip, but someone at 1600 Pennsylvania Ave. is burning the midnight oil.