It was useful to me to look at a card from the last decade and judge whether it was close to 7 years old (it was an Amex personal card, and is thus subject to the "lifetime" rule which appears to really be 7ish years). I would have no clue if I hadn't been in the habit of keeping all my old cards.
And though not that far back, there are a number of people who are kicking themselves over in the CIti AA Plat card thread in the Citi forum about not keeping track of whether a card was World or World Elite the time they cancelled it, cut it up, and threw it out, because after they did that, suddenly knowing whether it had been World or World Elite at the time of cancellation became vary important (as it's the "loophole" key to churning these cards much faster than 18 months).
And, btw, that's on the back of this particular card, so if you're going to just keep a photo of the card, make sure you get photos of both sides of the card!