Even if it was trained to drive like a human, it'd be better in many ways: It never gets drunk, doesn't get tired, doesn't get distracted, can drive old people (or anyone) around who shouldn't be driving anymore, etc.
"It can't be bargained with. It can't be reasoned with It doesn't feel pity, or remorse, or fear. And it absolutely will not stop, ..."
It would never leave him, and it would never hurt him, never shout at him, or get drunk and hit him, or say it was too busy to spend time with him. It would always be there. And it would die, to protect him.