Deaf people live in a permanent state of being deaf, and will develop coping strategies that normally-hearing people will not have.
Even with those coping strategies, it's clearly possible there are still some scenarios in which deaf people would fail to perceive an event or danger while driving, which a hearing person would notice, but we as a society have decided that's an acceptable level of risk because deaf people literally have no choice about being deaf, and it would be excessive to penalise them from being allowed to drive.
On the other hand, when a normally-hearing person blocks out their hearing, they are literally choosing to impair themselves below normal functionality and to drive in that condition, increasing risk.
Deaf people and wearing headphones are not the same argument.