Look, there is one on the I-15 between San Diego and LA. I go through it many, many times and have NEVER been stopped or even asked a question! The cars slow to about 10 miles an hour as you drive THROUGH the BP waves you and that's it.
Being a drama queen and saying that the BP are "asking for your papers, please" is ridiculous. IT DOESN'T HAPPEN. Again, I ask you....have you ever crossed one of these checkpoints yourself?
Not that I can recall. I drive 30-40 K per year mostly in the Southeast US. But I've been through many license/insurance checkpoints, which in my opinion are just as offensive as any other. A complete waste of limited law enforcement resources which should be reallocated toward real crime.
Then what are they for?