FWIW, I was asked to show my passport at customs specifically to see CBP sticker in it this week for the first time (ORD). He told me that I "should always hold my passport open to that page when handing in the customs slip" because they have to verify that. Dozens of exits so far, that was a new one. With some officers going rogue out there, it might be good advice for folks to make sure they go by and get the sticker.