As a former EMT, and a brand new diver, we were always taught as a first responder that your safety is paramount, and that you can't help someone if you get hurt or put yourself in trouble. Carrying that thought into diving, with my limited experience being 2 shore dives for cert, and 5 more shallow shore dives that week, I would not want to take a reg out of my mouth to give away if there was another option. Obviously getting a reg ripped out of your mouth by a panicked diver is out of your control, but that should be discussed during pre dive. If folks saying donate the primary because they don't know if the secondary will work, why even carry a secondary?