I can relate to this. The first time I encountered one of these machines, I had no idea what was happening (this was a good while ago). Now I always opt out even if I'm running late. I've had people behind me in line follow me in opting out because they did not know they could. I've never missed a flight because of it and have even gotten through faster than the person behind me at least twice (they had a long line going through). I think that opting out is a small statement but the people who see you do notice.