BUT: it is a pain you can't use your own bag and bag up as you go in some of them
You can, you just have to do it when the machine is ready. I work in Asda and our self scans allow you to add and remove bags during the transaction however it must not be when you are scanning something and you must only move things when the lights on the scanner are green. The red lights indicate the machine is either calculating the weight of the item just scanned or recalibrating the current "starting" weight if things have been moved off the scale so if you start taking things on/off while it is still halfway through the previous action then it will need an assistant to reset it manually.
It is the same as any machine - you can see you have just taken your bag off the scale and this is why there is a difference in weight but all the machine knows is that a minute ago there was 5 kg weight on the scale and so when you add that 250g tin you just scanned, it should weigh 5.25kg ... so when it only registers 3.75kg it will flag up a negative weight and will require an assistant to check it is genuine error and not an attempt to steal (and this does happen with enough regularity for it to be necessary)
You can't buy age-restricted goods without it calling an assistant.
So would you rather we just took all age restrictions off the self scan machines and hope customers are honest and don't abuse the system?
We'd soon be shut down when the 16 year olds use them to buy bottles of vodka and the 13 year olds use them to buy the 18 rated games their mum has refused to get them because they are not old enough. They would just wait till the staff are busy with other customers and then put their items through knowing that if they don't attract any attention from the staff then they can buy anything, unchecked.
There is no "back" button if you make a mistake, you have to call an assistant.
To make sure you're not abusing the system by scanning something, then cancelling it off but still putting the item in your shopping.
Also it's a practical issue = if you're cancelling an item off, if a member of staff has to come over to authorise the action then they can also physically take the item from you which means they can either be returned immediately to the shelves or put into the dedicated space for returns until someone has time to collect them rather than having items just lying abandoned all over the self scan area.
The theme, you still have to call an assistant so what's the point?
The point is that assistants are only required to intervene if there is an issue or there is a practical reason for them to be alerted to certain things happening.
So if you are wanting to buy a loaf of bread, some milk and the daily paper you'll more than likely go through without issue.
If you want to try and use a self scan for a whole week's worth of shopping then you're more likely to have issues (unless it's one of the hybrid machines that have the belt and larger scale area to accommodate a larger shop)
They really irritate me when I have my own bag, thanks, but there's already something in it which I've bought elsewhere. Even something small, or my umbrella. So I have to take whatever it is out before putting bag in bagging area, otherwise it thinks you've nicked something.
Again, it is because they are machines. All they know is that at the start of a transaction the scale should read zero, if bags are added then they are programmed to have a specific "normal" range it would expect bags to weigh. Anything outside of that is going to require verification from a staff member.
You know that when you put your bags on the scale you are putting a bag + an extra item on the scale. All the machine knows is that if you've pressed the "Use own bags button" you are using your own bag (which is calibrated to within a specific weight range, idk what the actual range is but lets say for the sake of argument it's between 0 and 100 grams) ... when it weighs your bag it comes to 300g which is significantly out of the weight range it would expect of just bags. Therefore it requires a staff member to visually verify that it's either just a heavy kind of bag (eg a rucksack not carrier bags) or the items adding to the extra weight is not the customer's shopping that they are trying to pass off as paid for items (and again, as a retail worker it happens more regularly than most people think). If we didn't have verification checks then