If you keep money (fiat) in your house, you can easily spend it, you will only noticed you spend it very fast. If you do not spend it, someone can know and invite thieves to steal your money. If thieves do not steal the money, the banks are still robbing you by decreasing the value of your money during inflation in a way that what you can use it to buy today, you can no more use it to buy the same amount of thing next year.
Another thing is that people that know how bitcoin works will have bank account because bitcoin is not for illiterates but for people that are literates and able operate phones and computers.
That's a naive thinking, if most people leave their money in their home, the criminals rate will increase really high since they know where you leave your money. Using this reason and saying become your own bank with Bitcoin isn't make sense, you're leaving your private key and your hardware wallet in your house too. Even the criminals didn't find it, they can just pointing their gun in your head and you will tell it honestly since you think your life is more important than money.
But it's not mean I want to say better to leave your coins on a centralized exchange, you need to find a way to hide your private key in a thing that no one expect.