It makes sense that there wouldn't be a lot of training data that consists of people admitting they don't know - forums like stack overflow wouldn't even permit

It makes sense that there wouldn't be a lot of training data that consists of people admitting they don't know - forums like stack overflow wouldn't even permit such a post/comment anyway. So presumably ChatGPT is very heavily weighted against giving "I don't know" as an answer when virtually all the examples of people asking questions in its training data are followed by plausible sounding answers.