Spoken like someone that never played or coached the game.
In all seriousness though, it is very hard to get motivated to play a team 2x in a year, and it is really tough when team A killed team B the first time around and is now playing them in a fairly meaningless game the second time.
Playing a team 2x in a season almost never happened up until CC games. I can only think of one time that a TO coached team had that happen in 78 playing OU 2x. The second time in the Orange Bowl NU scored really late to make the game look closer than it was. It really wasn't that close.
If you want to say that BP's teams take some opponents lightly, I will agree with that.
As far as not caring or having pride, or not enough respect for themselves to keep fighting I disagree with. Sometimes it really is like in the movie the "Replacements". Its like "quicksand" the harder you try the worse it gets. I know as fans we don't like that explanation, but as someone who coached for 20 years, I know it happens a lot more than we like to admit.