One of the main assumptions (nod to your etiquette story) is that people will behave in a civil manner. My son works retail at a big home imrovprovement store. Boldness in the shoplifting community thrives because they know the few monitoring employees can't do anything that physically threatens them, so they just load up a cart and run out with it. Another bottleneck I bumped into yesterday at self-checkout is security tags. I had to find someone who wasn't otherwise occupied to remove a device. Systems are systemic within their particular parameters. Adaptability is free in humans, expensive in machines.