The problem is any time you edit some of them out, you realize soon after that you don't have the one you need. If I don't carry around the cards I will need every day, I am likely to forget to take the ones I need only occasionally when I do need them.

The problem is that Coin doesn't really solve this. It only encodes credit cards; most of the other cards either don't have mag stripes or require other information on the cards than just what's on the mag stripe.