I never present my BA card at a check-in desk. I've had to flash it a couple of times, most often is when I am taking a guest into a lounge on the back of my status, the same for my LH card.

I also had to flash my BA plastic when I was checking in at DUB, they only had the one check-in desk open (monitor showed it was Club Europe but everyone was there) and the line was several dozen long. I stood to one side waved Silver plastic and the agent sent back the next people in line and called me forward. A tad 'DYKWIA' but I couldn't be bothered to wait for 40mins because they weren't properly staffed!

I've never presented my SPG card! Only use it to get the phone number off the back.

I have flown with a BA FF who used any excuse to flash his plastic Elite security line, check-in desk, lounge, coat check in lounge