Only time I really use the card is on the rare occasions when I have a difficult time getting my FF# on the reservation prior to check-in (e.g. sometimes when flying a partner airline and/or 3rd party booking). I find it easier to just hand over the card to the check-in agent instead of reading my FF# out loud.

I've never needed it to get into a OW lounge.

Not a big deal though. I'll just hang on to the most recent card that I have going forward.