As humans, we seek patterns even where none exist. My personal experience suggests that there is not much to it, but often I get surprised. If my villain takes a long time the first thing I think about is that he is most likely multi-tabling.
Many will take a moment to calculate pot odds
, or consult tracker info, but in my experience the number one reason is in tourney play, near the bubble, where shorties are trying to let some other guy, on some other table, bust before he does and get him into the money.