Nobody should, but we may have to in case the government seizes all our belongings.
If government seizes all your belongings (that is always a possibility) do you would still be able to function and think normally?
They could also reprogram your brain and extract any information and images you are hiding, with force or blackmailing.
Few days ago I watched one movie related with Project MKUltra, hypnosis and human experimentation could be used to extract any images you hold.
Funny thing about a memory, I can still remember some stupid things and songs from childhood but I can't easily remember a phone number or date.
Some people have better photographic memory but others are terrible in this, so not everyone would be able to use your system with images.
Better solution: Multisig and using multiple locations or even multiple countries for hiding your keys, and if all the governments in the world start to confiscate everything from people, than we all all screwed anyway.