I got off the FRA-SFO flight a couple. One of the first off the plane, thru immigration, to receive my bags me and 2 other fellows were the first at customs and all 3 got red folders.
With arrivals completely empty, it seemed obvious these guys were bored,looking forward to activities to make time pass.

Most often I am cruising thru, but then I am part of a larger group of pax lining up.

The interaction with the "red" dept. itself was quick and friendly: X-ray luggage, ask a couple of questions, done.