One of my relatives has just had his Barclaycard cancelled because he hasn't used it for quite a while and only keeps it for emergencies to use when on holiday abroad. . He applied to them for a new one and it was turned down.
I think increasingly credit card companies are getting very discriminatory about their customers and are not just turning down those who can't repay their debts but people like yourself who just keep some cards for emergencies. It might pay you to try and use them regularly, if only for small amounts, or occasionally to put a week's shopping or a petrol bill on them, just to keep them in use. Otherwise you might find that they are withdrawn and then they won't be any use to you, even for emergencies.