c152pilot,
I guess the main reason is because BA flight operations think there's little chance of someone becoming incapacitated between setting take-off power and the a/c reaching 80kts. As a result, no response to the 80kts call is there to reduce 'unnecessary chatter' during an important part of the flight. Furthermore, no response will prevent unnecessary aborts due to communication cock-ups.
The 80kt call is there as a trigger to remind us that we no longer "stop for any failure". As Sean Dell says, it also reminds NHP to select Reverse Idle or Full Reverse as necessary.
You've probably noticed the lack of incapacitation check at the other end of the flight as there's no response to the "100 above" call on an instrument approach.
I guess in BA we retire early so there should be less chance of us collapsing at work ....
