Some cards are just hard to find, even if they are numbered to a significant amount. I know they don't pack out everything they make, and 4-6% of print runs held back for replacements seems to be a consensus, even for 1/1s and such. And I strongly suspect they don't pack out the whole print runs in equal portions. While there's usually enough supply to not make people notice, sometimes it is. There might be 1990 Kile golds in a box somewhere, along with 1990 2009 Topps Heritage Chrome Jerry Hairstons and the Topps Chromes of that one guy who signed all color refractor autos but bases were never found, and the 2018 A&G Woods.