Some people just wouldn't go. Best estimates are that there were about 100,000 who stayed. Some were prepared most weren't. It was a mandatory evacuation order. Some wouldn't leave their flooded homes even when encouraged by the military.

One bar in the French Quarter stayed open and got national attention. They served their beer warm and by candle light.

One home owner in the Garden District, repeatedly interviewed by the press, vowed to fight rather than evacuate. He was prepared with food, water, guns and ammunition, fuel and a generator. His home was in a dry area and just couldn't understand why the authorities wouldn't leave him alone. (Ultimately that's just what they did.) 

A few folks sat inside their flooded homes and refused to leave when they were told their pets would have to stay.

Others stayed to help those who couldn't leave. A particularly poinginant story told of a man who collected (looted) groceries from the Whole Foods store on Tchopitoulas and distributed them to neighbors who couldn't get out. He carefully conserved the fuel in his car for this duty.