Because driving drunk shows that the pre-injury Jamie dealt the same type of callous disrepect of other people’s lives and needs that he shows after the accident.
It’s even worse than that, of course - at least (as far as we know) Jamie didn’t take any innocent people out with him when he had his accident.
In short: Had he not made the decision to be a drunk driver, he wouldn’t be paralyzed. Suing the doctor is nothing more than a transferance of guilt, a transferance he shouldn’t be allowed to make.