That is because those classic models are grandfathered in. Cars without safety features already were registered and existed when the laws were created, and it was easier for the DOT to just allow all vehicles manufactured prior to the law requiring safety equipment to remain the way they were and be allowed on the street.
That can be said about almost all classic cars. Like the article pointed out, you can still register and drive a Ford Model T in the state.
That is because those classic models are grandfathered in. Cars without safety features already were registered and existed when the laws were created, and it was easier for the DOT to just allow all vehicles manufactured prior to the law requiring safety equipment to remain the way they were and be allowed on the street.