MenschPress saidProbably sleep deprivation / narcolepsy / ADD. I have the same problem: I can't keep my eyes open during long speeches/lectures, no matter how interested I am in the speaker or the subject.
While I was working for the federal government as a natural gas economist in the 1970's, there was a proposal being considered for building a natural gas pipeline from Alaska to the lower 48 states across Canada.
One day, my assignment was to sit in on hearings assessing the impact of the proposed pipeline on Caribou migration patterns.
I had a great deal of trouble staying awake, since the topic took up the entire 8 hour day. Lawyers could easily take 30 minutes on a single arcane point of natural gas pipeline law. It sure killed any interest I had in becoming a lawyer.