> I had to wait for another human to verify my age, to purchase beer. The time before, I had to wait for a human to verify I had bagged all of my items.

So instead of 2 people to a register (one to bag, one to scan), you can have one person man 12 self checkouts? Sounds like an amazing reduction in labor. Even if self-checkout were half as fast as traditional checkout, that one employee is effectively serving way more customers per hour than they would be doing traditional checkout.