The vast majority of the folks who stayed were able bodies and they would have walked a mile or two from where they resides to the SuperDome. They had three days to do before the Hurricane hit. Those who were not able to walk should have called the police and they would have moved them.
Metropolitan New Orleans have 1.5 millions people, around 1.3 to 1.4 million evacuated before the Hurricane because they were smart enough to do so.