Trouble comes unannounced, nobody ever really knows when something bad might happen to you me us and our little brain. Sure, the idea of relying on memory isn't that bad, but depending only on it? That's just asking for trouble. Take me for example. I have memorized all of my social media passwords, some of them are over 50+ digits long. Sounds insane, right? I know. But I have read/used them so many times, they are basically on the tip of my tongue. Niow coming back to seeds, memorizing is not recommended because there is no backup way to gain access. You either know the seed or you don't. But with other sites there are other options for account recovery with like email, mobile. So, I don't think that's worth the risk anyone might be interested into taking.
I think our brain tends to remember more things that we prioritize, so suppose you had memorized a seed phrase, and you always repeat it (mentally, without saying the words out loud, after all, our electronics can hear us), this is a spaced repetition method, the chances of forgetting are minimized. Of course you should have backups written down in safe places.
Let me give you an example, you created a
Single-share Backup on Trezor wallet, you write down this single-share Backup in a safe place, after that, you upgrade your Single-share Backup to a
Multi-share Backup in Trezor Suite and configure it for a 2-of-3 scheme.
You'll try to memorize your single-share Backup while keeping the shares of your Multi-share Backup scheme protected in safe places scattered around.If you ever need to restore your wallet again, you can restore it using any hardware wallet that supports Trezor's shamir backup or software wallets like Electrum and Sparrow wallet. In this case, if you've already memorized your Single-share Backup, the recovery process will be much easier once you have memorized it well. You don't need to go around to get at least 2 shares from your Multi-share Backup scheme, you will only need to use them if you eventually forget the memorized backup.
Remember that I don't use Trezor's shamir backup, this is just an example, as the same can be done with BIP39 seeds.