Soldiers and cops have jobs that involve prolonged firefights, and they need all the capacity they can carry. Most civilians in "social encounters" fire only 2 - 3 shots.
I don't know if there is an authoritative reference on the subject, but I'll bet that most police shootings also involve only 2-3 shots per officer. The difference is that the distribution curve for police would tail off more slowly than that for private citizens.
