"Most carriers have never heard that advice, or ever given a thought to re-holstering their gun, whether on pocket or belt."
My experience is different….
According to a University of Washington study, three out of five U.S. firearm owners have received formal gun training.
In addition to professional formal training, there are other training and firearm education avenues that also provide good firearm handling and safety, like family, YouTube and range time.
I believe those civilians who choose to carry a defense pistol, by far the majority have been educated on the risks, safety, and legal issues. The majority also go a range for practice frequently.