ah, you've missed all my lectures on the subject!
Consider a card like a small SSD, there's a finite number of times that you can write to each cell before you start to get problems. and unlike SSD's where alot of the data on them is atypically static, cards typically get their entire contents flushed and re-written frequently. Also some cards have wear leveling, and some do not. it's not something they commonly mention either.
so it's just a bad idea to keep using the same few cards over and over, especially if you use your cameras frequently and take a ton of photos or video. To be fair, this is usually measured in years of use. it's not as if they'll die in 6 months, but if you tend to fill a card, wipe it and use it again, and do this over and over - just realize there are limits - especially with high capacity cards.
it's probably a good topic to discuss on it's own - sounds like an article in there. I may have to blow up a few cards to write it.