I don't know whose person would definitely memorize his private keys yet we do all know its alphanumeric compose of 64. Even just memorizing 10 of it would really be hard and tendency even just forgetting 1 letter or number would definitely lose up your wallet together with the balance inside it and how much more if you would need to memorize 64? It would be hard and the risk of losing money or tokens would really be high.Why would hassle yourself to memorize if you can simply write on a paper and keep it nor copy-paste into a notepad and keep it on a harddrive or any other means.