But is this official policy and they do not do it any more at all? I was told the same thing last year for a TK thru bags check. The agent said they cannot do it and I told that I only wanted to add my bags and not asking for a boarding card for that flight. They supervisor came and checked my bags in but told me that I have to get a boarding card from the joining airline.
The major issue that I see (its my opinion only) is that when the bags are thru checked without the passenger being checked in, and when the passengers do not show their bag tags when they check in for their next flight. So when they check in for their next flight, especially online and if they do not add the bags, it may not show that they have checked bags and so their bags may not travel with them.