Upvote:2
Long ago, when a check-in desk agent used to weigh and put the large tag on your suitcase, those little barcodes were separated and stuck on your case in various places. I presume this was to serve the baggage handling system in the event the main tag came off.
Only a few weeks ago, I flew BA from Heathrow (short haul to France) and used the automated bag drop. I asked the attendant what to do with the little barcodes. She said "Do nothing. We don't use them any more". Of course things may vary at other airports.