It's not just an AS thing. My father-in-law spent much of his life giving monologues that started somewhere and took so many twists and turns that no one could remember what the subject was. This guy would talk nonstop for 30 minutes or more, with no place for anyone to enter the conversation - because it wasn't a conversation, it was a monologue. So you're sitting there, forced to listen to his rambling speech about something you can't remember why he started in on it, nor figure out where he's going with it, and after 15 or 20 minutes you wish a hole in the floor would open up and swallow you. It's as though he had no internal editor, and was unable to summarize. He would start with something, and go off on incredibly wild, uninteresting tangents and verbalize everything he was thinking. And you can't just get up and walk away, you have to sit through it. This is why after having worked for 40 years and retiring, he has no friends out of all the people he used to know. And he's not malicious, just oblivious.
Fortunately, he doesn't do it anymore. His son had what must have been an ugly confrontation with him about it awhile back - glad I didn't have to witness it - but it seems to have made an impression on him, and he hasn't done it while we were there for a couple of years.