If it hasn’t been called, then STOPPING is still an option.
That is a very dangerous statement. IMHO, a wise pilot should never totally rely on the other pilot's speed call-out as a basis for such a critical decision as a high speed rejected takeoff. From observations in the simulator, it is rare that a high speed rejected take off on a limiting runway is conducted perfectly. In real life, that certainly is true. If there is a mistake on a limiting length runway, the chances of an over-run are high.
If a PM has not called V1 it could be for any number of reasons. That includes complacency or laziness, distraction (eg looking at an N1 reading which seems not quite right), fiddling with a thrust lever trying to get an exact N1 reading, and worst of all, momentary incapacitation. The decision to make a high speed rejected takeoff on a limiting runway length is probably the most critical life and death decision a pilot will make in his flying career. To base that decision on one man's verbal call-out rather than using your own eyes, is really stretching your luck.
There are some pilots, aware of the circumstances of previous accidents, that make the mental decision to go well below the calculated V1 even up to 15 knots below V1. They are playing the statistics i.e. the risks involved with a high speed abort versus the lesser chances of colliding with an obstacle during the lower flight path in the go situation. You have to be realistic here. The number of accidents that resulted from a high speed abort as against the number of accidents where trees and other obstacles were clipped during the second, third or fourth segment during IMC departures.