in principle, no software designer or traffic engineer can cope with 100% of situations and by dumbing down drivers, we create a situation where they are unused to understanding situations on the road and making judgements about how to react
I remember talking to an experienced traffic engineer at work and asking him why there wasn't a pedestrian crossing at a certain point, his response was that drivers didn't always recognise crossings and that they gave pedestrians a false sense of security, seemed like an argument for more crossings (familiarity) rather than less (unfamiliarity)
same point with unnecessary red turning arrows, I know that I have sufficient depth of field of view and gap judgement to know when not to turn against traffic, but the traffic engineer wants to protect me from myself
I'm a great fan of treating drivers as responsible adults, rather than as children and slapping them when they behave accordingly
http://www.seattlepi.com/transportation/293229_roads22.html