When I was in school, I often found class "boring" and "annoying" because the teacher was repeating things that had already been gone over more than once. (a major problem of our current public school system)
Even in college, I had the same problem.
I mean, in my Accounting classes I would get extremely annoyed with classmates who kept asking the teacher the same question over and over and over. Thankfully, since I was paying for it, I was free to leave and study ahead.
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I'm not saying the delivery has to be exciting.
But if the speaker doesn't seem interested in the subject, why should the listener be?
Now, Dr Hawking is the other end of the scale ... He would be so far above my head, unless he "dumbed it down" for me I would lose interest since I couldn't understand it. LOL