The assumption you have is that it's mostly a physical ability test. In many cases people don't know the rules or the reasons behind them. Right now, it's something like a 50 question test and you only need to get get 75% right. If you don't know what the proper procedure is up to a quarter of the time on only a subset of the rules, that leaves huge room for errors. I see it all the time with people passing on the shoulder and changing lanes in an intersection. These are high risk illegal activities that many people don't even know aren't legal because everyone else does it and cops rarely enforce it. I have yet to meet a person who doesn't give a shit about getting into an accident. Those people are more likely uninformed and overly cocky.