Katrina/Rita: why no Sec. 8 expansion?

FEMA reports temporarily housing Hurricane Rita victims under what sounds like another ambitious travel trailer program, while NMHC, still pressing for greater relief use of conventional housing, notes a Washington Post editorial in favor of spending government money on apartment rental vouchers instead of hotel rooms or "trailer parks destined to become dead-end 'FEMAvilles' far from urban centers and jobs."

The Post editorial poses a subtler question that readers here might want to help address: why did FEMA (well, FEMA and HUD really) choose to establish a new Hurricane Katrina rent payment program instead of expanding the existing Sec. 8 structure?