Hmmm. Interesting question. I agree with one of the others who answered here: showrunners, their writing team, everyone involved in show development, etc. want to grab people up front and generate interest…in attempting to do that, they might go for uptempo, hard hitting music, and credits that have an unusual font and behave like a power point presentation on steroids. But for the really exceptional shows (my taste runs to “Breaking Bad,” “Six Feet Under”, “The Sopranos”, “Dexter”, and more recently, “Bosch”, “Line of Duty”, “Longmire” and others of that calibre) I think great pains are taken to “match out” the credits with the tone\mood\vibe of the show. Interestingly, with Dexter, which is coming back in the fall after 10 years, the opening credits (I read) will CHANGE ENTIRELY, because the series itself will have a different setting, cast of supporting characters, etc, By the way, I don’t want to misrepresent myself. I am not in the business or anything. Just a content enthusiast and, um, armchair critic.