How do you know what you don't know?
At the same time, I think you are realizing what is meant by "The more you know, the less you know."
Then too, Steve brought up a good point. Many use "I don't know" as an excuse to not take responsibility. I've been guilty of that. A lot of us won't bother to learn or find out anything beyond what will just get us by and we settle for that and keep ourselves in a rather easy spiritual kindergarten, as Bill called it.
Jim