And the bottom line is that safe gun handling, the fundamentals of marksmanship, the array of skills to effectively use a firearm defensively in an unpredictable, dynamic, violent event, and the knowledge to appropriately make a decision to resort to lethal force are neither instinctive nor intuitive. Such skills and knowledge need to be learned.
Someone having "grown up around guns" is no guarantee that he (or she) has learned all, or even some, of it.
"It is long been a principle of ours that one is no more armed because he has possession of a firearm than he is a musician because he owns a piano. There is no point in having a gun if you are not capable of using it skillfully." -- Jeff Cooper