In response to your primary question “Calling a Dive - Should this be part of instruction?”. I feel that the answer is a resounding YES. In fact, of the two agencies’ whose programs I have been privileged to teach, this issue is addressed. However, I do feel that this point is not emphasized nearly enough.
You are correct in observing the reasons why dives are not aborted even though conditions are (or may be) beyond the skill level of the divers involved. However, allow me to suggest a few additional reasons. Ego, which goes hand-in-hand with “ there is the perceived pressure to continue”. Additionally, the ever present economic pressure to continue the dive. Lets face it, dive boat charters are not cheep. And if the dive is cancelled, both divers and boat crew stand to loose money, depending on the refund policy. Remember, even though conditions might be ok for more advanced divers on the boat, conditions might not be ok for “everyone” on the boat.
Some instructors simply state, rather briefly, that the diver “agrees to only dive in conditions that are as good as or better than the conditions in which he/she was trained” or words to that affect. Other instructors, more correctly, will go into detail about the process a diver should use to determine what the diving conditions are and if they should be diving at that spot and at that time.
I realize that, as instructors, we can not make every decision for our students once they are certified and out diving on their own. I do believe that, as instructors, we need to give them the decision making tools that are necessary for them to make the correct choices with regards to the go/no go question. Because when it comes right down to it “each diver is ultimately responsible for his/her own safety and survival” so they need to be well equipped to make good decisions in this regard.