I put my traders in pin bags because I like showing as many pins as possible. I have a mesh pocket in between the pages in my pin bag, so I put the cards that go with the pins on the page before it inside the mesh page. There are mesh pages in between every pin page, so it is easy to do and not confusing. Yes, it takes time to look for the card, but it is only a matter of minutes if there are only 50 cards to look at. I feel these type of bags keep the pins more protected and the cards more mint. The problem is finding these type of pin bags now.
Every now and then, they are on ebay for pretty decent prices. They used to sell them at the parks and everywhere, but now, they have been replaced with pin bags that have flimsy pages, so I do not recommend those, because they are too floppy and the pins can hit each other etc., not to mention how hard it is to put your pin in these new ones. The old ones had this plastic lining that kept each pin page stiff, and everything stayed in place.
Before 2008 or so, a lot of us never kept the pin cards, but with the scrapper and counterfeit issues, it is wise to do so.