The brother-in-law of the man who told me this is a retired NYC police officer. The retired cop is also a bad shot.
Seriously, I think that many officers just think of the sidearm as another tool, like a radio or a nightstick. They don't consider that it's a tool that needs a heck of a lot more training than just memorizing a bunch of radio codes, and regular practice to boot. The qual should be just a starting point, not the finish line, but as long as the rank and file have the attitude that barely making the minimum score is "good enough," they'll be lousy shots.
Friend of mine (also a gun collector) is an officer in a local municipal department in a little town outside Atlanta. He told me about an encounter between a fleeing armed robber and a couple of their department's officers . . . they cornered the guy in an office park parking lot, and the shooting commenced. So far as the internal investigation could determine, a total of about fifty rounds were fired (two 9mm mags for each of the cops and however many the bad guy had on hand for his Lorcin, say 10) and NOBODY hit ANYTHING except a nearby dumpster which had two holes in it (maybe they were fresh :-o ). They didn't even hit the bad guy's CAR. Apparently he surrendered out of ennui.
My friend's a good shot. All the gun nuts at my job went down to the local range on our lunch hour a couple times and put a lot of lead through paper. He and I were neck and neck, with our Naval Reserve guy coming in a strong third. I think he edged me out at 25 yards . . . (darn!)