It's often too late for cabin crew to take action. Passengers checking in online make their first contact with BA staff at the boarding gate. The ground staff at BA are seriously reduced and facing constant demotivational change. Getting large heavy bags off passengers at the gate causes delays which are attributed to the ground staff. Better to let the bags onboard and allow the cabin crew to have any blame for delay attributed to them. Departmental targets equal a broken approach to the required end result. A safe on time departure.
I have moved bags forward to be off-loaded only to find the door closed and the jetty retreating from the aircraft in the rush to sit in a queue for take off. Nobody wants the blame for a delay attributed to their department.