I guess I'm just wondering if there's data on how often you these self-checkout bottlenecks. The way other commenters describe it makes it seem like it's fairly often. Hence the surprise.
Although I agree just-walk-out scales well with demand.
> The way other commenters describe it makes it seem like it's fairly often.
There's almost always a line at them when I walk by in the stores in my area. Usually, the line there is about as long as the lines at the manned checkouts.
In fact, just follow the logic down that road. Consider highly-volatile demand purchase scenarios. A company might over-spend on self-checkout stations to cover high-demand scenarios that go unused on more typical days. A more efficient approach is to avoid requiring additional stations to cover changes in demand. Just create a single system (walk out purchasing) that handles all scenarios and be done with it.