The only situations I've been in where it helped were international, as others have said. Back before I had any status, a colleague got us into the priority lane at SCL. The gatekeeper refused to let us go to the check-in window even though her boarding pass said "elite plus" (or whatever it was back then); he wanted to see the card. Finally the desk agent overheard and waved us forward. Could have been a Spanish-English thing, but the card would have helped. I still carry mine.