I love those self checkouts!
I try to use them as often as possible. Only thing is here at the local Wallyworld, there is a 25 item limit. I asked why, and the clerk told me it was something to do with the system, and it got bogged down after too many items.
The limit that is imposed may have something to do with the fact that the platform where the "bagging" is done actually weighs the goods. At least that is the way that the self-checkout works at my local Shop-Rite. This was designed to prevent a customer from placing an item in a bag without having scanned it, but the systems can easily become confused. The system knows how much a particular item weighs, and if that added weight is not added to your bag promptly, the system detects this as an error on your part.
If you don’t place a scanned item in a bag fairly quickly, the system posts an error message that sometimes requires a clerk to intervene. And, if you try to rearrange things in those bags, all hell can break loose with the system.
Clearly, the developers of these automated systems wanted to assure the merchants that there would be a way to detect customer pilferage, but the systems are not totally perfected at this point. I think that one of the weaknesses of these systems may be that they have a limit on their weighing ability.