It has been required extensively in Asia. SQ, TG, CX, MH, BR, FD, KE, OZ.... have all either asked me to see the card, or at least had it mentioned on the T&C that the card may be requested. The requirement to show the CCrd seemed to be lodged in a text entry in the PNR notes.
SQ, CX and MH all had a form you could complete and visit or scan and email your CCrd for verification (along with license or passport scan sometimes).
Regarding the text entry in PNR notes, I know this as when visiting the THAI office in Seoul, once the card check had been completed, I asked for a document to subsequently provide my to son, and was given a long telex-style print with the specific section of text highlighted with something like " CCRD CHK: CCRD VERIFIED SEOUL OFFICE DDMMMYY".
It all seemed so archaic.....especially since there is no check if using an OTA. Maybe airlines were being defrauded in Asia more than we might expect....