Young men and women do not stop driving too fast until something terrible happens. Lebron shrugged it off, but life is a hard lesson sometimes. Speeding puts everyone in danger especially people who are not good drivers.
Have you ever stopped to consider what is the optimal speed limit? Obviously, getting in a car and driving in public can be life threatening. However, society seems to be comfortable trading a certain amount of risk for a certain amount of convenience. So how did they arrive at the current speed limits? Are they really the best balance between safety and productivity? Think how safe everyone would be if the max speed limit in America was 10 mph. I guess I would argue that speed differential has a lot to do with safety. Nowhere is that more aparent than in Miami. They seem to have the biggest range (from old people driving 40mph to coke dealers in Ferrari's going 100mph). Meanwhile, in Michigan, everyone seems to be in the 65-80 range. There is another thing to consider as well. If speed limits are set unrealistically low, then everyone gets in the habit of breaking the law and enforcement becomes a selective exercise. This creates a bad atmosphere for all involved. I would argue that the 55/65/70 limits on the US highways are unrealistically low in most cases. It would seem that about 80% of the drivers are breaking the law, at least by 5 mph, because they know that it will be tolerated.
All of the 55 stuff came in during the original oil embargo in an effort to increase fuel economy by slowing people down. And you certainly burn less gas and produce less pollution at 55 than at 70. Top speeds in Europe are around 78 (130 kph) with 66 and 54 mph zones based on road type. 78 is only around on limited access divided highways.