NDs are gonna happen. For somebody, somewhere, sometime. Not everybody. We can only be responsible for ourselves. Personally, I plan never to have one and I take the precautions everyone else already covered. But, I've seen too many people over the years have brain farts at the worst times ...
Anywhere folks handle firearms frequently and routinely, especially in the course of their jobs, work under great stress and sometimes don't get enough sleep -- NDs are going to happen to someone. Not to everyone; not to most people. Nor will they necessarily happen often, but they will happen. Can we control the rates of NDs within our families, units, departments or agencies? Of course. Training. But can we do away with 'em completely? That's the goal, of course, but ...
Had a buddy who was a USMC rangemaster who'd spent a lot of years on the range -- he told stories that were almost unbelievable, but sadly, too true. Worst one I ever saw was a new female (not that gender was the issue here) m.p. candidate sweep a range NCO with an off-safe 12-gauge during a practical fire ... then pulled the trigger and sent 00-buckshot into the range cover. Needless to say, she was looking for a new career field the next day.
It's easy for the average gun owner who doesn't carry/use guns every day for 12 or 24 hours a day, 7 days a week, doesn't have mandatory qualification every month, only takes his/her guns out for recreation, and then only after a full night's sleep on an easy day off to say: "It'll never happen to me." But the reality is that, unfortunately, sometimes fatigue, adrenalin, alcohol use, lack of training, lack of knowledge about a particular gun, just plain stupidity or one of those totally inexplicable brain farts followed by an uncharacteristic physical reaction will cause an ND. And in occupations such as law enforcement or the military where very high volumes of personnel are being trained, shooting high volumes of ammunition and often under less than optimum circumstances, the odds are against doing away completely with the phenomenom of the ND.