They can catch legitimate mistakes. I had this happen about a week ago. I scanned something, thought I heard the beep, then put it in the bag. It stopped me and replayed the video. I looked at the item list and sure enough, it didn't scan. It was an honest mistake, and the camera caught it. I rescanned it after the attendant cleared the error.

I've also had it flag when it thinks there is more stuff in my cart when going to pay. This happened to me when I had an umbrella in my cart. The attendant had to come over and clear it. When I worked at a grocery store 20+ years ago, checking that there was nothing on the bottom of the cart was a big thing for cashiers; the cameras seem to automate this check at self-checkout.

I've also had if false flag when I pass my hand over in a way that looks questionable, where the attendant has to come review the video and clear it.

All this stuff happens in real-time during the checkout process.

For people who want to steal, they seem to find ways around it. I was at the store a couple months ago (the same one that has all the tech mentioned above) and the beep next to me sounded ever so slightly off. I looked over, the guy was on the payment screen, which I'm assuming disables a lot of the camera checks, and was passing all his items over the scanner and making the beep noise with his mouth. The tone wasn't perfect, but it was really close.

Primarily used to catch and ban from the shop heavy repeat offenders, some people shop lift on order and resell items versus use them for them selves, or have addiction problems with alcoholism etc.

There's usually one person in charge of an array of self-checkouts, and the self-checkouts flag suspicious activity.

> I don’t see what the cameras add.

Again, stores would not spend money on self-checkouts and cameras if they didn't pay off.