This limit certainly applies in Europe for health and safety of baggage workers. One man lift below 23kg and 23kg-32kg bags should get a heavy label and only should be lifted by 2 handlers. Over 32kg things that can;t be broken down smaller need special handling. The airlines are charged more for a heavy bag - so usually limit to FF or premium classes or charge for overweight. But despite being paid more per bag, I reckon the ground services don't enforce the 2 man lift and put the pressure on the individual handlers to get the job done. I guess if a handler hurts themselves on a 23kg+ lift the employer has no liability although morally responsible.