A boarding pass screams: I'm a non-member trying to get in on status and international travel!
It does?
I'm a UC member and I can't remember the last time I used the card for access to a UC.
If the scanner is placed within reach, I just scan my own boarding pass, and if not, hand the boarding pass to the agent, they scan it, and I'm on my way. Works just fine at least at MSP, ORD, IAD, EWR and DEN.
Very occasionally I'll get an agent who wants to ask about my itinerary before scanning the boarding pass, and I just say, with a little pleasant authority, "I'm a member, just scan it.", and they do. (Make sure you've mastered your pleasant authority voice first lest you trigger us vs. them.)
To me it screams, "I have this piece of paper which will make your light go green."
(I do carry my card in my travel bag, but only for additional insurance with international *A partner lounge dragons.)