Negligence probably. But these incidents of unholstered striker-fired weapons seems to be happening with increasing frequencies. Are newbies made aware of the danger with an unholstered weapon? It seems that ignorance might be a major factor in these incidences.
It seems that the gun community needs to emphasize that every handgun should always be securely holstered (or in a proper hard case) when being transported or carried. Is this being taught in LTC class or NRA courses?