Checking board passes at the door has/can have multiple functions:
To make sure that your handling agent's people on fast food wages haven't sent you a passenger who should be be boarding from the adjacent gate.
To be able to say "Down this aisle and your seat's on your right" instead of having a passenger heading to the sharp end instead of the blunt end and having to scramble over the seats because he/she is in the aisle for HJK and has an ABC seat
To be able to say "Welcome on board, Mr RevMan2" (if you're a Qantas purser).
And - by the way - is this REALLY a problem?