I cannot store a million dollars in my brain. I can with a branwallet.
but most people don't want to store anything. Most people, if they had $1,000,000, would go buy the things they want and then rely on the safety the government affords them. A house, some cars, blah blah, next thing you know after all the legal processes are done and they have everything they ever needed/wanted, they have completely forgot about Bitcoin because it's just not practical.