Too many bags being opened is a problem because every time a bag is touched, someone could introduce a bomb into it. Why do you think they have these announcements in the terminal to never let your baggage out of your control? And yet here we are allowing ever more people access to the bags that are out of our direct control.

If the bad guys aren't afraid to die, then they aren't afraid to get caught either. One bad guy gets a job as a baggage screener, brings twelve devices to work one day and explodes twelve airplanes. What difference is it going to make then if you have a video recording of him doing it?