It seems like a standard thing in Asia, though enforcement is patchy. EVA's policy is to ask for sight of the credit card, but they only seem to bother 50% of the time. However, Pacific Airlines (a LCC based in Vietnam) never ask and its their policy not to ask. (I have a friend who regularly uses my CC details to book flights for herself or her mother... I never fly with them or go to check-in.) In Europe I've rarely been asked. Sometimes the cardholder must fly, sometimes not.

When I couldn't find my card for checking in for SQ to LAX at Taipei, the agent said she didn't need sight of the card - she just needed me to tell her the last 4 digits. (This seemed to subvert the system somewhat - if I'd obtained someone's details to make the booking, I'd could still have those details to hand to provide them at check-in!) I ran through 3 different sets of 4 digits before "bingo".

EVA told me if I did forget them, it wouldn't be a problem because I could sign an indemnity form. I wonder if SQ would actually deny people boarding when everything else is in order.