The rarity of plane hijackings is balanced by the decades of harm they can do, even beyond the obvious death and destruction. 9-11 for example led to 20 years of ruinous war, trillions wasted, and many lives lost, not to mention geopolitical realities which led to even more death and loss of money. Taking extreme caution to prevent a recurrence of that, not to mention protecting lives and a whole industry, probably doesn't compare to upskirt shots.