The governor of Louisiana was on camera stating that President Obama was welcome at any time, but the state has received everything they presently need from him, from immediate financial aid, FEMA's constant presence, and daily communication from/with White House officials; therefore, the President's visiting the state now, although welcome at any time, as he said, would detract from the rescue and other significant operations due to the logistics, costs, and freeing up Highway Patrol, etc., regarding security. There have been residents who've expressed disappointment that he has not visited, but the governor stressed the importance of attending to priorities at the present time.
(And guess who showed up for photo ops?)