Why should they get a pass when D has made a good enough play thatbthe QB was being forced to dump it but they don’t get a pass if the pass is just simply incomplete ?
The argument is very subjective. When he is throwing it away, he is acknowledging defeat (for that down), and is voluntarily, consciously, and deliberately giving up any possible yardage gain, and the down. When he throws it to an area with a chance of being complete, he isn't "giving up," so his team is to be held to a higher standard.
Very subjective, but, that, I believe, is the philosophical concept.
Robert