Society benefits if we have smart people in all jobs.
The main point of The Bell Curve was not really about race. Rather, Murray and Herrnstein were lamenting that the great IQ sorting machine was pouring our smartest people into a smaller and smaller number of occupations. This is a loss to the rest of society.
Which is why I think it is such a bad idea for the New London, CT police department to reject a potential officer because he scored too high on an IQ test. They argued that smart cops will get bored and leave, so it is not worth hiring and training them.
Police work, of all work, requires constant judgment calls about how to best use the great power of the state. It requires more smarts than the average job.
Moreover, the leadership of the police department will eventually come from the new officers working their way up the chain of command. No smart patrol officers now means no smart captains later.