Moreover, in case of death, amnesia, accident that makes you unconscious for the rest of your life, or whatever extreme yet real-life possibilities, will there be anybody else who's able to unlock that encryption? Or will the coins perish with you?
I remembered something from o_e_l_e_o.
Other answers above have told you just how insecure brain wallets are and how humans are a terrible source of entropy.
Each year:
69 million traumatic brain injuries:
https://pubmed.ncbi.nlm.nih.gov/29701556/12 million strokes:
https://www.world-stroke.org/assets/downloads/WSO_Global_Stroke_Fact_Sheet.pdf10 million new diagnoses of dementia:
https://www.who.int/news-room/fact-sheets/detail/dementia5 million new diagnoses of epilepsy:
https://www.who.int/news-room/fact-sheets/detail/epilepsy2.5 million cases of meningitis:
https://www.path.org/articles/toward-world-without-meningitis/2 million new brain tumors:
https://academic.oup.com/noa/article/3/1/vdaa178/60433151.5 million cases of encephalitis:
https://www.sciencedirect.com/science/article/pii/S0163445322002110That's
each year, and that's only major conditions which directly affect the brain. Add in things like cardiac arrest, heart disease, sepsis, shock, diabetes, vascular injury, hemorrhage, poisoning, smoke inhalation, etc., all of which can cause secondary brain injury, and there are literally hundreds of millions of people every single year who suffer some form of insult to their brain which can lead to memory problems.
Do you want to trust all your coins to those odds? I know I don't.