We have the tech to do this. They library system where I am put RFID tags in all the books. You put the all books you want in a special tray at checkout. (There is still a checkout counter with a machine.) The computer will instantly display all the books you have on the tray. You touch the screen to confirm all the books and it will check them out and print a paper receipt.
They can probably eliminate the checkout too, maybe. I imagine that they do it so that the user (you) can confirm what items the computer thinks they wanted to check out.
Once you want to checkout, you drop everything you bought into a big bin near the checkout area - it calculates the total based on all RFID tags, you pay, take everything and leave.
Imo this is better than checkout in the carts - don't need to attach a payment POS and carry bags to every single cart lol.
I do remember doing this as well at Decathlon.
However, because RFID chips are too weak to be reliably read in bulk and at a distance, you need to deposit your items one by one in a special trough that scans them. And this is only possible because both Uniqlo and Decathlon are 100% house brand and can thus ensure the chips are present in everything, which is why random corner stores or supermarkets can't copy them.
My guess is that that the time savings aren't large enough to offset the cost for stores with lower-cost goods (especially since most time-intensive products in a supermarket are things like produce that needs to be weighed and self-service pastry).
You do need to put the items in a box at the exit to pay (you can't just walk out of the store with the shopping cart), but no manual scanning.
Edit: should have refreshed the page before commenting, Decathlon and uniqlo are popular here
The idea does not fail in countries with labour shortages. Even with increased shoplifting- it is simply too asinine employing people sitting on their ass all day scanning groceries. Labour costs real money here.