In this case it appears he had a truck but no license. Seems like taking the risk of getting pulled over and cited for driving without a license is preferable to drowning in a 13ft high storm surge, for me at least.
A risk calculation that's easier for us, seeing the aftermath, and having nothing at risk.
It's hard for people outside the experience of poverty to understand it. It's not just a ticket if you can't afford to pay it, and can't afford time off work to fight it in court.
He could possibly be out on parole or similar, where getting pulled up for driving with no licence or registration could get you sent back to jail.
For many of these people, even if they have a driver's license, the cost of gas and a hotel room is insurmountable. Many have their entire extended families close by so there isn't a cheap "stay with relatives" option that isn't also in the evacuation zone.
During that kind of an evacuation, the cops have worse problems than checking licenses. The risk was probably pretty small, at least during the evacuation itself.