I frequently encounter issues at self-checkout where I scan an item, hear a beep, assume it's added to my total, but the previous item hasn't registered on the

I frequently encounter issues at self-checkout where I scan an item, hear a beep, assume it's added to my total, but the previous item hasn't registered on the scale yet, so it doesn't add the item. These systems are often rigid, hard to use, and differ between stores. Sometimes, customers are blamed for theft, but it's not always intentional. Many struggle with these systems. Why can't they make self-checkout user-friendly?