In the USA the implementation of self checkout varies wildly, and seems to be linked to the socioeconomic condition of the neighborhood.
Grocery shopping in rich neighborhood = scale has a large tolerance and will not stop you from continuing to scan if you place something unexpected on it. You can scan and bag in whatever order without the machine making any accusations.
In a poor neighborhood = you scan an item and put it on the scale, then put your bag from home on the scale to bag the first item. The scale is set to a strict tolerance and stops scanning items “UNEXPECTED ITEM IN BAGGING AREA” and you have to wait for an employee to unlock it.
As they say “there’s nothing more expensive than being poor”, and bad self-checkouts is just another factor in that.
In Finland in some shops you can take a barcode reader and bag the things directly as you go. In the automated counter you just put in the scanner and pay.
There are no scales and nobody would notice if you just don't scan the item. In theory there are "random" checks. I've never seen one happen though. Not having a huge desperate underclass makes many things a lot smoother.
Grocery shopping in rich neighborhood = scale has a large tolerance and will not stop you from continuing to scan if you place something unexpected on it. You can scan and bag in whatever order without the machine making any accusations.
In a poor neighborhood = you scan an item and put it on the scale, then put your bag from home on the scale to bag the first item. The scale is set to a strict tolerance and stops scanning items “UNEXPECTED ITEM IN BAGGING AREA” and you have to wait for an employee to unlock it.
As they say “there’s nothing more expensive than being poor”, and bad self-checkouts is just another factor in that.