Once had someone ask why airliner cockpits don't have side rearview mirrors like cars as it can be rather difficult to see the engines from the flight deck, especially in the smaller members of the family (737). And another time it was airbags in the yokes to protect pilots from serious injury during landing/takeoff incidents resulting in a crash.
As mentioned by OK465, the A340-600 has these to aid in taxiing and manouvering.