There are times when you really need them. Desk agents who control access to airport lounges are one example, with some airlines' agents not accepting any other form of evidence (including frequent flyer elite status that their own computers printed on your boarding pass not ten minutes previously). I generally pull any I think I'll need out in advance of a trip and put them on the pile with my passport, left-over foreign currency from the last trip to that country, the Oyster card for London, maps and so on.