Earlier quoted context omitted.
I avoid self-checkout because the entire machine is usually set up around the assumption that I will try to walk out of the store without paying for one or more items, or by futzing the bar codes so that I pay $1 for a $30 beef roast. The self-checkout technology will never improve as long as that assumption remains. If you can't trust the customer to not steal a pack of gum, you can't trust the customer to not steal…
If we put an RFID tag on every item and use an RFID gate then we would just have to walk past the gate which is capable of detecting every item without you having to take it out of your cart or bag. A turnstyle could then force you to pay and disable the RFID tags. Cost and transmission distance of passive RFID tags are the major obstacles, I believe.
Remember, the store is more interested in protecting its operating margins than in providing more convenience for the customer. If the technology does not allow a store exec to believe that it can stop a $30 steak from walking out the door unpaid, it will never be installed.